Riot caches user count too aggresively

[tkolo]

Description

Channel user count appears to be cached by riot. The cache seems to be somewhat broken as the count can get out of sync and it's clearly riot not homeservers, as after using "clear cache and reload" button everything returns to normal.

Steps to reproduce

I'm not sure, here's a link to discussion on Linear supporters channel that led to discovery of this bug:
https://matrix.to/#/!eUGMvloIjhBoAwlyRh:matrix.org/$1521470613962zFfsX:kolosowscy.pl

Version information

• Platform: Doesn't seem to matter, I've got this bug on both web (firefox) and android version.

[t3chguy]

It being fixed by clear cache and reload could also be the homeserver not sending membership updates via the incremental syncs

[t3chguy]

Since you have the bug on two entirely different codebases then it's less likely to be riot than the homeserver