Room Avatar regularly switching to old version

[stefanheinrichsen]

Description

In one of our rooms we face the following issue:

Every now and then the room avatar switches to an old version. It seems this mostly happens during longer inactivity times (e.g. you notice the old version in the morning when no messages were send during the night). Once a new message is send it updates on the given client to the recent version.

It seems not to be related to a specific client (we tried at least Element and Fluffy) which leads us to the asssumtion this is somehow related to the synapse.

Steps to reproduce

• Join the affected channel (#chat:matrix.un-hack-bar.de)
• Wait until the avatar changes

The room avatar is usually red and only during our open times green. Still it often shows green without a channel event changing the image.

Homeserver

matrix.un-hack-bar.de

Synapse Version

1.146.0

Installation Method

Docker (matrixdotorg/synapse)

Database

Docker-Image: postgres:17-alpine, single DB, no restores made, ported from SQLite years ago (but still the same DB)

Workers

Single process

Platform

Running on a VPS by Hoster Contabo (12 cores, 48 GB RAM)
OS is Debian 13.3/trixie with Kernel 6.12.63+deb13-cloud-amd64
Running Docker Engine CE 29.2.0, plenty of free RAM and CPU time

Configuration

Mostly default. Rentention is enabled with

default_policy:
   min_lifetime: 90d
   max_lifetime: 555d

Relevant log output

We could not check log files as it is superhard to correlate the time of the icon switch in the client apps to the log file output.

With additional hints about how to filter/do the timing correlation we might be able to provide something.

Anything else that would be useful to know?

This behavior first appeared after we switched room version to 12 end of November. In the former room we never had such issues.

One of us noticed that we had a script sending an "invalid" room avatar event via REST after the new room was created (see attached msg.txt; note the type being "m.room.avata" with a missing "r" at the end). However we are absolutly unsure if a broken transaction can cause such issues. We would expect such a transaction will be ignored by the server or by the clients. So this is mainly guessing from us...