Tweaked from my posts to the linux ut3 email list:
Just came on a short term workaround for this that allows your server to stay advertised in the server browser... The issues happen just after a map switch (on my setup, at least), so I tried to stop them from happening: I set GoalScore=0 and TimeLimit=1440 (minutes in 1 day). We've been up for two hours straight this way! Beats locking up every 20 minutes.
As long as no one leaves the server
and then returns, this seems a fine workaround... I am still hanging the thing in the usual manner when I exit the server and then rejoin it. If you think about it, this is precisely what a mapchange does, so perhaps this makes sense? Who knows...
Latest update:
I did a restart on my server (ApocTestbed1) around midnight eastern, and I was able to join it again 7 hours later when I woke up (score was 44-8 at the time, so it had been running), so all looks good, or as good as can be expected! (unless I join it again...
)