I don't really use gitlab, but I wrote my own git implementation recently (https://github.com/oridb/git9), and I've had bug reports when people tried to use it on gitlab.

Apparently it can deadlock processes on the server, stopping the clone -- and they never get cleaned up. While they don't prevent anyone else from using the machine, they do sit around wasting resources, and potentially causing a denial of service attack.

I figured out bugs for github's issues, but I haven't been able to find one for gitlab's, and they've been pretty silent on the bug that someone else filed about this as far as I can tell.

It didn't feel like a particularly easy to trace system when I tried debugging.