I have never heard of that type of behavior before, and it shouldn’t have anything to do with CPTUI’s code specifically.
Any help I’d be would require having a lot of elevated access to try and recreate and then debug what’s going on, and I do prefer to avoid requesting that much access when I can help it.
Wish I had a better answer here. Best suggestion I can think of would be see if it still happens when the install is barebones and perhaps only CPTUI active. If it doesn’t then I think some other plugin or theme code may be interfering here.
It’s a strange one for sure. We tried removing all the plugins except CPT UI, and it was still doing it. The plugin has been trouble-free until lately so wasn’t sure if a WP conflict occurred.
I’ll try a clean install