It can lock when you are doing maintenance on the database but it should clear on a retry. We can't cure it because there are times when the database really does lock as a result of the running PBX doing an update, the most common being the time-segment update which runs every 5 minutes. The lock should only live a very short time but if you catch it then you will get bounced. I'm looking at making it a little more graceful in 4.
Best
S