often it doesnt finish the quest.

That happens alot when the group I´m assigned to has made the first part without me already. Today I had to do a quest 4 times... the last time I was alone and finally it finished.

Since that happens we shouldnt be assigned to instances where a part of the quest has been finished already...

Hit "O" and go to the "Team Options" tab. There you can select the option to not join an "open team"

I´d rather have them fixed that bug because I´m not playing an mmo to be playing all alone

The rules for auto-teaming only allow players to join the map within the first 2 minutes and if the objectives are still uncompleted.

To track down issues where you are encountering this - we'll need to know the exact mission where this happened as we need to investigate if the first objective can be completed prior to the cutoff.

Please submit a mission bug - select the misison you are on - and explain that auto-teaming put you on a map with completed objectives.

i have had this a few times myself, though only with missions that involve scanning objects.

I can confirm this error, had it a few times

I've had this happen a few times, and most of the time I noticed there were multiple Ops buttons on the edge of the screen. Once each one of these has been clicked through, usually I was able to complete the mission. However, the issue still stands that this is not very obvious and this doesn't fix the issue every single time.

Indeed there was always something to scan, but cant recall the mission anymore. I remember two missions where it happened... one I´ll come to soon on my 2nd toon, but the other....

type /lfg and you'll never be made to join a team again... it has solves 90% of all problems I've had with missions.
the other 10% was solved by never clicking "not now" when a BO asks me if I want to warp out.

Last time it happendI belive it was a quest in the Vendor System. Just a plain patrol quest.