On several occasions recently we have been noticing a problem with the Duty Finder which appears to occur when you click Commence very close to when another player clicks Withdraw (which, unfortunately, continues to occur frequently as tanks look for duties which are in progress). This causes the following to occur:

A party member has withdrawn from the duty.
Finding new member.
A problem has occurred with the Duty Finder server.
Please try again in a few moments.

You are then dropped from the DF queue and forced to queue up again. I observed this again today when I happened to be queued into the same party as my partner. I clicked Commence, received the error and was kicked from the queue, but as he had not yet clicked Commence he was able to remain registered for the duty. Being kicked from the queue because of this was quite annoying, as I was put to the back of the queue again.

I have seen some users claim that this happens repeatedly for them until they restart the client. I have not experienced this problem - I was able to successfully queue up again and perform the duty.