We encountered this bug in a normal protean fight against Alibi, Alibi just teleported into the middle pillar and would not get out of there again. After a bit of searching from us we found her below the pillar and were able to shoot and kill her from there, but she still did not teleport back out even while we were shooting at her.
Platform: PC
In the following clips you can see the issue. In the first i am just running around the pillar where she is stuck in, in the second you see the position from which we were able to shoot her.
Twitch Clips from livestream part 1: https://clips.twitch.tv/TenaciousApatheticCoyoteDogFace-oPvinrP0vObvffY0 and part 2: https://clips.twitch.tv/MuddyDependableFlyImGlitch-7GTs-ZnDYlMdT725
I hope this help, if more information is needed, just tell me.
Cheers, Mats