I attempted two dungeons this morning, but I had some very huge problems in them. These all happened over different attempts:

In total, 3 people's character models just stopped in place and wouldn't move, but looking at the map I could see each of their blue circles where the action was, fighting enemies. In addition to this they were taking damage and if I ran over to their models I could see them performing attacking actions, even though from my point of view the models were just standing still very far away from the action while attacking the air. I could target their character models only, but if I tried performing an action on them it simply told me they were out of range.

In total, 2 people's models simply disappeared. I couldn't see them at all but I could see the attacking animations (like the archer's arrows) and they were receiving damage. If I looked on the mini-map they weren't on it, but if I looked on the actual map I could see their blue dots.

On top of this, every few minutes the dungeon would simply freeze for about 5 seconds. All character models stayed still for this long except for mine and any actions I performed seemed to all stack and occur at once when it fixed.
These are very huge problems, but it's made even worse if I tell you that I was meant to be the healer. Note that other than the 3rd one which I've had a lot since the 28th of August, none of these problems have occurred outside of dungeons before. At least not with party members.

Thanks.