So, I've found the group finder to be utterly broken. I think the problem might be caused by people queuing for dungeons whilst still being in a group, where one or more of that group are offline.
It puts you in a group of 7 (or sometimes 6)... and then you are actually unable to leave the group. It just won't let you leave at all. Can we fix this nonsense please? If you are truly planning on punishing anyone leaving a group - then this needs fixing ASAP because it's going to frustrate a LOT of people who play with a limited game time window due to real life.