Fenrir invincibility bug (only bots)

[torpid vector]

So recently ive noticed that a bot fenrir with a full build has a bug that is very annoying and gets you killed (by them) more times than not. Basicly if you do a lot of damage to the fenrir, and then stop firing for a short while, they will become completly invincible, but they can do damage to you, and it will result in me dying more than half the time when fighting fenrirs

[wary acorn]

I noticed that fenrirs have a "shield"...?
It looks like a bulwark ability but without the blackhole on top, so its barely noticeable