Sigh...
@1 Crash
not UTF related, if you order "switchlevel" during map switching process (game has ended) your command interferes with the automated servertravel, don't complain that you crash then, your own fault!
@2 ini messup
not UTF related either
http://www.oldunreal.com/UnrealReference/unicode.htm
@3 hidden ID
Ah finally something that -IS- UTF related. It's true when a server is paused you can't see new players (on the new scoreboard) that join while the server is paused. Explaining why etcetc would take ages, but it has todo with delayed initialization of the graphic components which are prone to fail if they are initialized immidiately. Solution: don't pause the server

I have thought around other ways of initialization but didn't come up with anything reliable AND crashsafe, so the given solution is a compromise.
However, it is possible to use admin commands on them, the ID is given, you just don't see it. Since IDs are incremented each time, just add +1 to the last known ID and you have the ID of your newly joined player. It adds +1 each time he rejoins (IDs are NOT restored by the UTF stats recovery).
Don't worry about the CUID in your user.ini, because if you don't have one, you just get a new one next time you join a UTF server.