Intermittent Issue: Form Data Not Clearing Between Journeys

[ebadian]

Describe the bug
When a user completes a journey and attempts to start a new one in the same browser session, the form is occasionally pre‑populated with data from the previous submission. This does not happen consistently, which makes the issue difficult to reliably reproduce.

To Reproduce
Steps to reproduce the behavior:

1. Complete the full journey once.
2. Start the journey again from the beginning in the same browser.
3. Observe that, intermittently, previous form data is pre-filled.
   Note: The issue occurs sporadically and may require multiple attempts.

Expected behavior
All cached or stored user state should be fully cleared, ensuring each new journey starts with an empty form.

Screenshots
N/A

Repository

• Runner

Desktop (please complete the following information):

• Browsers: All

Additional context
Using cache.drop() is unreliable for clearing Yar sessions because it target the underlying catbox cache, which isn't part of Yar's public API and may not consistently remove the session entry. Yar only guarantees behaviour through its own session methodsUse request.yar.reset() instead — it's the officially supported way to fully clear a session and ensures Yar handles both cookie + server‑side storage correctly.
The clearState function in cacheService currently uses cache.drop. This may not fully clear the session state. It may need to explicitly reset Yar using:

request.yar.reset();

Note:
here is the Yar api documentation.
https://hapi.dev/module/yar/api/?v=11.0.3

[jenbutongit]

Probably difficult due to it not being repeatable but could you please confirm that the webhook response is successful? And that the cookie session_id is not changed?

And if possible attach an example form.

Could you also confirm your infrastructure for this? are you using redis? or using the in memory store?

[calum-ukhsa]

Probably difficult due to it not being repeatable but could you please confirm that the webhook response is successful? And that the cookie session_id is not changed?

And if possible attach an example form.

Could you also confirm your infrastructure for this? are you using redis? or using the in memory store?

Webhook response is successful, and the application connects to an Amazon ElastiCache (Redis) cluster for in‑memory data usage, accessed over the internal VPC network.