In matrix.org rooms when using a matrix.org account, spam removal/redaction events often don't sync at all even hours later

[ell1e]

Description

In matrix.org rooms when using a matrix.org account, spam removal/redaction events often don't sync at all even hours later. This seems to be a server bug since it seems to happen to multiple people with multiple clients. Since some spam is highly disturbing depending on the images sent, this seems like a notable problem. Deletions really should always sync even if there's a delay, but this doesn't seem to be the case.

Steps to reproduce

1. Witness a mass spam event of 20+ spam messages, often containing disturbing media, in one of the bigger matrix.org channels.
2. Eventually some admin will start deleting messages. You're almost guaranteed to still see 10% of them hang around forever, apparently often stuff other people will report was deleted on their end.

Homeserver

matrix.org

Synapse Version

Command doesn't complete on matrix.org right now.

Installation Method

Docker (matrixdotorg/synapse)

Database

matrix.org

Workers

I don't know

Platform

matrix.org

Configuration

No response

Relevant log output

The matrix.org admins should have that.

Anything else that would be useful to know?

No response