Player not teleported into instance (although he is displayed as in the group)

Ok. I'll take your word for it. I just saw the thread, thought I had some info which might have been relevant and shared.

You had new info .
The voteinvite did not exist when I opened this thread .

Oh dear. I didn't even noticed the date on it. It still being on the first page I assumed it would be current.

Technically, it still is current since the bug still exists. Anytime someone gets stuck on the loading screen, that player ends up in the instance by name but not physically part of the instance. Happened to my girlfriend last weekend when entering the Watchtower Containment Facility. I told the other two players not to re-open and invited her to the instance once she closed out of the game and re-logged.

That is fortunate.
I have been in groups where the stuck player ignored all my chat demands to relog... mostly in PvP. It suck to loose a match because of that!