Gitlab is remembering settings when deleting and recreating group

I created a group on my gitlab CE omnibus server. I was fiddling with the settings on that group, and somehow I did something that made it so when I tried to access the group I got a 403 error (using my admin user). I couldn't figure out how to fix the problem.

So I deleted the group and tried to recreate it. Every time I create a group with that name, even if I make the visibility "internal" and don't change anything else, I get a 403 error when trying to access the group. But if I create a group with a different name, it works fine.

It seems that there's something in the system that has remembered information about that specific group name. To try and figure it out, I made a backup, fully extracted the tar, and extracted/uncompressed all the files in the backup. Using grep, I cannot find the group name in the expanded version of the backup.

This is weird and extremely frustrating.

Omnibus installation of 11.6.3 on Ubuntu 18.04, using the gitlab package repository.

Further weirdness: The group name that I was trying to create is "tristar". I just tried to create groups named tristar2, tristar3, and tri3 and they all immediately give the 403 error. But I can create a group named "aaa" in exactly the same way and that group works perfectly.