There are multiple Lockdown parties that cannot be Spectated.
When I was in queue for a Lockdown game, I tried joining a few of the groups, but they all made messages in my chat that said something along the lines of "Oops! ...". For some reason, I could not withdraw from queue and was stuck in queue. The problem was I wasn't even in queue (even though the game said I was) and no more "waiting" messages popped up in my chat as well. I tried to get rid of queue by going into the Arcade. Guess what? I was still in queue! I couldn't change my gear or change my loadouts. The only fix I see is by logging off and back on. Please fix this strange bug.
I also have the same problem. It happens randomly, sometimes even when I press "play again" after a match.
In my case it does display the message that my game has been delayed, but never actually puts me into a game. Like it literally queues people who sign up way after me leaving only 1 waiting (ie. me). When I try withdrawing, I get an error message.
I have to restart the client every time. Fortunately the in-game mail returns my entry fee.
I don't understand how updating the game for a PvE event creates bugs in PvP. You might have some fundamental design flaw somewhere.