Nextcloud mail desyncs very often

[UltraBlackLinux]

Steps to reproduce

Not quite sure but I'm running into it all the time.

Just received some emails that put an unread badge onto a mailbox, and I couldn't see them until I force-refreshed the mailbox.
Another mailbox also had an unread badge but there was no unread mail, even after refreshing.
The drafts mailbox often desyncs very badly, showing drafts that don't exist (showing an error when trying to delete them), or not showing ones that do.

Expected behavior

the UI should always reflect the current state of the mailbox

Actual behavior

it doesn't, mails are often invisible until the mailbox is force-refreshed

Mail app version

4.0.9

Nextcloud version

30.0.2

Mailserver or service

Hetzner

Operating system

AIO Docker image on linux

PHP engine version

Other

Nextcloud memory caching

No response

Web server

Apache (supported)

Database

Other

Additional info

Not sure about some of those. Using an up-to-date AIO container