Partly diverging states between different servers in a room

[JokerGermany]

Description

Since a couple of days we have a PARTLY Diverging states between servers.
We noticed it first on

2024-08-11 11:04 CET

e.g. matrix.org.

This messages never got to tchncs.de
https://matrix.to/#/!PQOOuZmmjzGoXWzKuZ:tchncs.de/$I8n-Ot7dx_w_Xg07Rj1Lwi_kJ7N167DctLUtIYbPu0g?via=tchncs.de&via=matrix.org&via=envs.net

(Source)
You see here unable to load:

(Source)

https://matrix.to/#/!PQOOuZmmjzGoXWzKuZ:tchncs.de/$W5zQbZ5x_LbgYHyKnegqP0l3kZp4we3Ocp22oBAKmZk?via=tchncs.de&via=matrix.org&via=envs.net

looked just before the ban, both see join but see different events
thats even more curious

Someone in the room even noticed, that it's a three way split
https://matrix.to/#/!PQOOuZmmjzGoXWzKuZ:tchncs.de/$UCr8mZSzVRSJDnVRzd6n7xChRo0brDFQSJ1U8XHguDg?via=tchncs.de&via=matrix.org&via=envs.net

2024-08-16 22:58 CET

today the problem was noticed again:
The user robbit9:matrix.org never joined the room from the tchncs.de perspective:
https://matrix.to/#/!PQOOuZmmjzGoXWzKuZ:tchncs.de/$oBns-h9wOWuTPLVhLVU94S20n6NXVZCUyGwSuo-o8W8?via=tchncs.de&via=matrix.org&via=envs.net

His spam messages never reach tchncs.de
https://matrix.to/#/!PQOOuZmmjzGoXWzKuZ:tchncs.de/$b54m5JO9VEtdJ9HGRv5YZui-D_FgB1nYY0Q817EpOlU?via=tchncs.de&via=matrix.org&via=envs.net

(left side matrix.org, right side tchncs.de)

This makes it impossible to moderate the room.
Spammers from matrix.org are spamming the rooms and the messages don't "reach" tchncs.de therefore draupnir isn't able to ban them and delete the messages.

Perhaps a workaround would be making a room upgrade, but perhaps you can look into the bug to fix it and make Matrix better =)

Steps to reproduce

don't know...

Homeserver

matrix.org, tchncs.de

Synapse Version

1.112.0 (2024-07-30)

Installation Method

pip (from PyPI)

Workers

Multiple workers

Platform

Linux

[JokerGermany]

Looks like
https://matrix-org.github.io/synapse/v1.38/spam_checker.html
is the reason.