Hi!
I’ve done some studio recordings over the weekend and stacked all the drumtracks in subtracks. Some takes wheren’t played until the end of the song, and as a result, some files aren’t as long as others. Back home i’ve startet group editing my drumtakes and BAM: “the tracks aren’t completely in sync, group edit may fail!”. And it does. 
After one hour derping around in the arrangewindow i might find a solution to this ‘bug’:
Groupediting still works when all subtracks in the folder are opened! 
Then it is not problematic if a single file have a different endpoint. However, all my takes have the same startpoint. Maybe that’s a thing… 
If someone has the same problem, and my solution works for him/her, please report back in this post. I really want to sort this out and hope i’m not just lucky…
btw: i’m on 7.5.3.
Cheers, and happy comping!
Tomess