what version of Mustard do you use?

@Algernon Whistlewright But it's not a picture. It's only posting pictures that doesn't work.

Are you guys able to load replies in #Mustard? I get a connection error.

Damn. Something's wrong with my instance then. It's very unstable, too. Always hits the DB connection limit.

Nope, everything seems to be fine with the db.

what about cd to your main friendica dir then:

php include/poller.php

it should complete (after a time) with no output. If there is output those are errors.

@Beni Keller Do you have a VPS or shared hosting?

@Mats Sjöberg I'm on Uberspace.de - it's a shared host but with a lot of extras. But they only allow 20 simultaneous connections to the mysql db. This should be enough, right?

Sounds like it should be enough, but hard to know... If you are running a recent version of Friendica (recently pulled from git master) you could try disabling the StatusNet conversation completion. That process is a bit heavy. You can do that by adding this line to your .htconfig.php (note the dot-file, there's also one without the dot!):
$a->config['system']['ostatus_poll_interval'] = -1;