Is there any reason as to why it's doing this so I can perhaps prevent it? Seems to be happening regularly.
Done it twice in the same queue now... 23 minutes on a 16 minute average wait time. Seen it fill up twice.
1) Let's say you have 9 DPSers, 3 healers, 1 tank in your queue. You were the last one to join. A group that were in progress killed the the second boss, then after the boss was down, 8 DPSers, 3 healers and 1 tank leave the group (very common thing). The system tries to fill that group. It takes the people who were queued before you, you get reset.
2) Let's say you entered an LFR dungeon in progress. You killed last boss. Now you want to kill boss 1 and boss 2. So you queue for the same wing again. The system will try to put you in a fresh run. Let's say while waiting, a group in progress kills second boss, many people leave. The people in your queue fill that group. Since the system is trying to put you in a fresh run, you don't get taken to kill 3rd boss again. You get reset.
3) The queue system has some sort of disconnect protection. So let's say there is a group being formed it already had 17 DPS. You queues as DPS. The one of the 17 DPS got disconnected, you got his place. But because the system reserved a spot for him (for a short time), when he logged back he got his spot and you got kicked out.
4) There is always the possibility of a bug.