Caldav syn from ZOHO calendar does not sync all items

[prosperot]

Since the last 2 updates, syncing from ZOHO calendar via davx5 skips items. When calendar appointments are created (on my macbook via ZOHO calendar or Apple Calendar) all new items are synced via davx5 to my samsung S23. But a few sync moments later, some of these items are dropped and no longer synced (and also not anymore shown in the syn log). They are however still visible in Zoho calendar and on my macbook, but not anymore on my Samsung S23 (that uses davx5 to sync).

[ggikthuo]

I am experiencing similar issues. I'm using calendars at zoho.eu. Individual appointments are missing from the calendar (aCalendar) on my Samsung S23 with DAVx5 from time to time. Despite reviewing the log file, I have not been able to determine whether this is due to DAVx5. However, I have now noticed that the DAVx5 accounts under ‘Synchronise account’ display the message ‘Synchronisation disabled for all items’? The ‘Synchronise now’ button is greyed out. I have checked the usual tips for synchronisation (battery optimisation, energy-saving mode). Interestingly, newly entered appointments on the Samsung are transferred to the Zoho calendar. What could be causing this behaviour?
Any hint would be appreciated.
Georg

[prosperot]

It looks like davx5 doesn't pick up all ZOHO calendar appointments that need to be synced. And as these appointments are missed by davx5, they are also not shown in the davx5 logfiles.
Must be a davx5 problem, when using onecalendar (with build in Caldav sync) on my Samsung S23 I don't have these problems.

And yes new appointments are synced, but somehow after a day or two, they are not sycned anymore and they are removed from my samsung calendar.

[rfc2822]

Is there any way to reproduce that problem? I have tried to reproduce that behavior with Zoho and latest DAVx5 and couldn't reproduce it.

Or maybe some hint about which events I have to create?

Without being able to reproduce the problem, we can't have a look at it.

Must be a davx5 problem,

Absolutely possible, but also possible that it's not DAVx5. Different client can use different methods to fetch events (and also use different time limits etc). Often only the method that is used by DAVx5 is broken. So would really need to reproduce the problem.

Can you also try to set the "Past event time limit" in the DAVx5 to empty (not 0)? Do the missing items then appear?

[prosperot]

Well to reproduce it:

Add multiple items to your Zoho calendar of mulpiple days
Then syn them with davx5 on your android device (in my case a Samsung S23) and check if you can see the items on your samsung calendar (or a calendar) . In the davx5 logfile thet are also visible.
Check again a few days later and you will notice that some Zoho items are gone in your samsung calendar (or acalendar) . They are however still visible in your Zoho calendar. In the davx5 logfile these items are also gone.

I tried setting the Past event time limit to 0 but can still see Zoho calendar items that are not synced by davx5 (but are visible on my samsung when using eg onecalendar (that has a build in Cavdav syn option) and my macbook (that also uses Caldav sync)

[prosperot]

It takes days, not hours, to reproduce. After a few days you'll notice the problems. Many other above have reported the same behavior.

[rfc2822]

Yes and that also means that it may take weeks/months to debug, if I have one try every few days. Also the server is really broken so I don't see a realistic chance to debug/fix/workaround that.

[SmartlyCautionMaybe]

Adding in case this helps: I'm experiencing the same issue. I uninstalled DAVx5, which (correctly) resulted in the calendar showing no entries. I then reinstalled DAVx5, and reconfigured all the synchronization settings. I also set the "Past event time limit" setting to be "All events will be synchronized".

When I force a synchronization, DAVx5 indicates "something" is happening for a couple of seconds. then stops. However, no calendar entries are synchronized (calendar is still empty).

I am able to access all calendar entries via both the Zoho android app and the Zoho website.

My environment:
Pixel 7, running current version of GrapheneOS
DAVx5 version 4.5.9-ose
Calendar app: aCalendar+

I have been successfully using DAVx5 with this environment for at least the past three years, and have not experienced event 'drops'.

Again, hope this is useful.

[rfc2822]

I also set the "Past event time limit" setting to be "All events will be synchronized".

Thanks for your report. However, when you set this setting to empty (All events will be synchronized), DAVx5 uses Collection Synchronization and the server doesn't report any events anymore (which means the server is broken). This is already stated on https://www.davx5.com/tested-with/zoho.

So you can only use Zoho with a non-zero "past event time limit".

I wonder whether I should take the time and efforts the report the Zoho issues and where. Do you think there's a reasonable chance that somebody actually reads the reports and that things become fixed?

Do you know where to report such things?

[rfc2822]

I have sent two reports about the ETag and collection-sync issues to Zoho. Now waiting for their reply.

[ggikthuo]

Hi Ricki, I opened a ticket at ***@***.*** 9 month ago with this problem, because I thought it's on behalf of Zoho. I closed the ticket that time, because in a sudden after reconnecting the calendars it worked well and I couldn't reproduce the error anymore. The support was friendly and helpful, so you should give it a try. Georg Am 13.03.2026 um 09:14 schrieb Ricki Hirner:

…

I also set the "Past event time limit" setting to be "All events will be synchronized". Thanks for your report. However, when you set this setting to /empty (All events will be synchronized)/, DAVx5 uses Collection Synchronization <https://www.rfc-editor.org/rfc/rfc6578> and the server doesn't report any events anymore (which means the server is broken). This is already stated on https://www.davx5.com/tested-with/zoho. So you can only use Zoho with a non-zero "past event time limit". I wonder whether I should take the time and efforts the report the Zoho issues and where. Do you think there's a reasonable chance that somebody actually reads the reports and that things become fixed? Do you know where to report such things? — Reply to this email directly, view it on GitHub <#2041 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIUCT63DQEA3RRWKJR2EG4D4QO7M7AVCNFSM6AAAAACWCVLS6OVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTMMJRGI2DIMY>. You are receiving this because you commented.Message ID: ***@***.***>

[SmartlyCautionMaybe]

Hi Ricki -  I'll second that Zoho support is friendly and (most of the time) responsive.  They do at least seem to take bug reports seriously. Here's my suggestion: If you could draft up a description of what you believe is causing the issue and publish that in the forum, we (as end users) could use that as the basis for opening our own tickets with Zoho.  That might help get attention because: There would be many people reporting the same issue, and  The reports are coming from their own (paying) customers)  Thoughts? Until recently DAVx5 has been bullet-proof, and I like being able to use 3rd-party calendar and contact apps, so I'm hoping we can get this resolved quickly. Thanks. From: ggikthuo ***@***.***> To: ***@***.***> Cc: ***@***.***>, ***@***.***> Date: Sat, 14 Mar 2026 02:07:29 -0600 Subject: Re: [bitfireAT/davx5-ose] Caldav syn from ZOHO calendar does not sync all items (Discussion #2041) Hi Ricki, I opened a ticket at ***@***.*** 9 month ago with this problem, because I thought it's on behalf of Zoho. I closed the ticket that time, because in a sudden after reconnecting the calendars it worked well and I couldn't reproduce the error anymore. The support was friendly and helpful, so you should give it a try. Georg Am 13.03.2026 um 09:14 schrieb Ricki Hirner: I also set the "Past event time limit" setting to be "All events will be synchronized". Thanks for your report. However, when you set this setting to /empty (All events will be synchronized)/, DAVx5 uses Collection Synchronization < https://www.rfc-editor.org/rfc/rfc6578 > and the server doesn't report any events anymore (which means the server is broken). This is already stated on https://www.davx5.com/tested-with/zoho . So you can only use Zoho with a non-zero "past event time limit". I wonder whether I should take the time and efforts the report the Zoho issues and where. Do you think there's a reasonable chance that somebody actually reads the reports and that things become fixed? Do you know where to report such things? — Reply to this email directly, view it on GitHub < #2041 (reply in thread) >, or unsubscribe < https://github.com/notifications/unsubscribe-auth/AIUCT63DQEA3RRWKJR2EG4D4QO7M7AVCNFSM6AAAAACWCVLS6OVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTMMJRGI2DIMY >. You are receiving this because you commented.Message ID: ***@***.***> — Reply to this email directly, #2041 (comment) , or https://github.com/notifications/unsubscribe-auth/A5S5CZUEBHLQKG3UICBH4LT4QUHMDAVCNFSM6AAAAACWCVLS6OVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTMMJSHA2DCNY . You are receiving this because you commented.

…

__________ David Horton

[rfc2822]

To me it is very strange that it would be a Zoho problem, syncing using aldav from Zoho to my macbook of onecalender app gives zero problems. Only syncing using davx5 does.

Well from my side every other server works, only Zoho makes problems.

So this argument doesn't lead anywhere in my opinion. We'd really have to reproduce the problem and determine what is causing it.

Today I'll sync with Zoho in the emulator again, like every day. Couldn't reproduce the problem since I try to … Update: couldn't reproduce today

[SmartlyCautionMaybe]

An additional data point to consider: I installed the "Calendar Sync" Android app over the weekend, and so far it appears to be doing flawless CalDAV syncs between Zoho and aCalendar+.

I'm still using DAVx5 for CardDAV contacts syncing, which has always worked just fine.

Very strange.

[rfc2822]

Unfortunately that doesn't help – neither to reproduce the problem, nor to determine the actual problem :/

All I know is "DAVx5 is said to be broken" but I don't have any reference point where I can start.

[prosperot]

I know that you can not reproduce it, but after testing with 'calendar sync-trial' i now have items that are prefectly synced using "calendar sync-trail" but are not synced using davx5. I can reproduce this on my zoho calendar and samsung s23.

[rfc2822]

Today again added test event in my test account (for 17 May), synced with DAVx5, events were updated properly. No missing events. Updated event, synced again, success. No missing events.

[prosperot]

I am giving up on this bug. Apparently it can not be reproduced by some. So I am moving to CalendarSync that works flawless

[rfc2822]

Btw status update: I already have reported two server bugs in a very detailled form (took a while to write these reports). One is said to be fixed, the other one is pending and I'm waiting for their reply.