This bug happened at least three times with my newer characters below lvl 50 so far after the Stonethorn patch, PC-EU. Queueing solo for a random normal, ending up in a group for some vet dungeon, unable to port in as I'm under lvl 50.
I also saw other lowbies auto-added into the same group as me in some of these cases. Everyone eventually realizes there's no way for us all to start the dungeon, and the group falls apart with everyone having to wait 15 minutes before they can queue again.
It felt confusing when it happened the first time, by the third this is quite frustrating. Can we please have a fix for this, or at least a post acknowledging the issue? Thank you.

I also found an older thread about this in a different section which had no recent posts, so I figured I'd post in the Bug Reports part for better visibility. Thread link:
https://forums.elderscrollsonline.com/en/discussion/544587/df-puts-my-low-level-tank-in-veteran-content