sometimes we use an out-of-date server for send_joins

[richvdh]

... which in turn means that the joining user gets a very old view of the room state

[richvdh]

For example, when one tries to join #megolm:matrix.org, matrix.org returns the following list of servers in the room:

• dmp-develop.com
• matrix.freelock.com
• darmstadt.ccc.de
• jki.re
• onedefence.com
• terracrypt.net
• sw1v.org
• matrix.org
• exul.org
• t2l.io

Of these, dmp-develop.com is offline. I don't know why we don't use matrix.freelock.com. Anyway, I've seen various servers use darmstadt.ccc.de. But that server left a long time ago. So the user gets an ancient state and timeline snapshot, and it takes ages for backfilling etc to sort it all out.

[richvdh]

Of course if the user sends any encrypted messages while the server is trying to catch up, then it will exclude any users who joined the room since darmstadt.ccc.de left.

[richvdh]

Another example: if you try to join #riot via hveem.no, you get a room consisting entirely of a single 'create' event. :/

[richvdh]

Fixed by #3899