stopped getting new events from room, can't rejoin it

[zephryn]

Background information

• Dendrite version or git SHA: still on 0.3.8
• Monolith or Polylith?: monolith
• SQLite3 or Postgres?: sqlite3
• Running in Docker?: nope
• go version: 1.15.8 linux/amd64

Description

a few days ago i noticed that a room i was in wasn't receiving new events.

when trying to leave the room, i get the following error:

Error leaving room
User "(matrix account)" is not a member of room "(id of room i can't join)"

attempting to rejoin the room returns a different error:

InputRoomEvents auth failed: eventauth: eventauth: "(matrix account)" is not allowed to change their membership from "leave" to "join"

this message is similar to the one shown in issue #1023.

trying to rejoin also produces these logs server-side:

level=error msg="helpers.CheckAuthEvents failed for event, rejecting event" func="processRoomEvent\n\t" file=" [github.com/matrix-org/dendrite/roomserver/internal/input/input_events.go:106]" auth_event_ids="[(event id)]" error="eventauth: \"(matrix account)\" is not allowed to change their membership from \"leave\" to \"join\"" event_id="(event id)"
level=info msg="Error authing soft-failed event" func="processRoomEvent\n\t" file=" [github.com/matrix-org/dendrite/roomserver/internal/input/input_events.go:120]" error="eventauth: \"(matrix account)\" is not allowed to change their membership from \"leave\" to \"join\"" event_id="(event id)" room="(id of room i can't join)" type=m.room.member
http: TLS handshake error from (client-side ip goes here): EOF

[zephryn]

short update on this issue: these room errors came and went for a while in two rooms i was in and have not reoccurred for about a month now. not sure if the issue was resolved with a new release or if it just happened to go away after some time.

[kegsay]

Possibly related: #1662