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Bug: Custom HTML Block Breaks Dacast Video Playback After Recent Update #79022

@movieversalfilm-web

Description

@movieversalfilm-web

Description

Following a recent WordPress/Gutenberg update, Dacast iframe embeds no longer play video correctly when inserted via the Custom HTML block.

The video player loads and displays the poster image/thumbnail correctly. Audio plays normally when the Play button is pressed. However, the video image remains frozen on the poster frame and never starts rendering moving video.

This issue affects both newly embedded Dacast videos and previously working Dacast embeds that functioned correctly before the update.

Step-by-step reproduction instructions

Steps to Reproduce
Create a new Post or Page.
Insert a Custom HTML block.
Paste the following Dacast embed code:

<iframe src="https://iframe.dacast.com/vod/ce90b24a8ea4d52a5018b9958f1e1fcf/ca119dff-558d-41ac-9cef-38f61cba7116" width="100%" height="100%" frameborder="0" scrolling="no" allow="autoplay;encrypted-media" allowfullscreen style="position:absolute;top:0;left:0;"> </iframe>

Publish the page.
Open the page and press Play.
Expected Behaviour
Video playback should begin normally.
Audio and video should both play.
The poster image should transition to the video stream.
Actual Behaviour
Poster image remains frozen.
Audio plays correctly.
No video frames are rendered.
User hears audio but only sees the static thumbnail/poster image.
Additional Testing Performed
Confirmed NOT to be the Video File

The Dacast iframe URL was opened directly in a browser:

https://iframe.dacast.com/vod/ce90b24a8ea4d52a5018b9958f1e1fcf/ca119dff-558d-41ac-9cef-38f61cba7116

Result:

Video plays normally.
Audio plays normally.

This suggests the video file and Dacast player are functioning correctly.

Confirmed NOT to be Theme-Specific

Tested with:

Astra
Twenty Twenty-Five

Issue occurs in both themes.

Confirmed NOT to be Content-Specific

Tested using:

Existing Dacast embeds that worked previously
Brand new Dacast embeds

All exhibit the same behaviour.

Plugin Testing
Yoast SEO temporarily disabled.
Spectra not installed.

Issue persists.

Observation

The Custom HTML block interface appears to have changed recently and now includes a redesigned editor interface.

The issue began immediately following this editor/UI change.

It appears that the updated Custom HTML block may be interfering with third-party iframe video rendering.

Environment

WordPress Version: [Please insert]

Gutenberg Version: [Please insert]

Theme Tested:

Astra
Twenty Twenty-Five

Browser Tested:

Chrome
Edge

Hosting Provider:

IONOS
Impact

High.

This issue prevents Dacast-hosted movie trailers and video content from playing correctly on production websites.

Audio continues to play, but video playback is effectively broken.

Additional Notes:

Issue occurs with both Astra and Twenty Twenty-Five themes.
Yoast SEO disabled during testing; Spectra not installed.
Dacast iframe URL plays correctly directly in browser.
Issue occurs on a completely blank page with only the Custom HTML block.
Custom HTML block interface updated with new look and options in WordPress 7.0.

Screenshots, screen recording, code snippet

Image
<iframe id="ce90b24a8ea4d52a5018b9958f1e1fcf-vod-ca119dff-558d-41ac-9cef-38f61cba7116" src="https://iframe.dacast.com/vod/ce90b24a8ea4d52a5018b9958f1e1fcf/ca119dff-558d-41ac-9cef-38f61cba7116" width="100%" height="100%" frameborder="0" scrolling="no" allow="autoplay;encrypted-media" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen style="position:absolute;top:0;left:0;"></iframe>

Environment info

Google is Version 149.0.7827.54 (Official Build) (64-bit). Astra Version: 4.13.4, WordPress Version 7.0, Windows 11 Version 25H2 (OS Build 26200.8524)

Please confirm that you have searched existing issues in the repo.

  • Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

  • Yes

Please confirm which theme type you used for testing.

  • Block
  • Classic
  • Hybrid (e.g. classic with theme.json)
  • Not sure

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    [Block] HTMLAffects the the HTML Block[Type] BugAn existing feature does not function as intended

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