This has been happening since the last patch went live. I’ve only seen it when queing in a group. After all members of the group have picked a role, the queue doesn’t start and we have to keep exiting/entering queue and trying to change roles until it finally starts the queue. Sometimes the queue works fine first try, and sometimes we get the bug. Group size doesn’t seem to affect it, and neither does someone picking flex queue.
Happened to me also. Unlocked the situation each time by promoting another member as group leader.