[solved] Can't deal damage to unique monsters sometimes [PS5]

Some unique monsters (the yellow ones, mobbosses) can't be damaged on some spots. If they walk away from the particular spot attacks deal damage. Than again there stuck in a spot where they can't get damage.

E.g. there is a unique monster with a blue shield. I throw grenades and shoot at it. First shot damages the energie shield. 50+ grenades of all sortes don't do anything. I walk away shoot some other mobs. Get back. No damage dealt.
Trying to get it off the spot. Throw grenades. It loses half life. Stands still again. Doesn't get damage until it walks to another spot.

Yellow monsters are rare, not unique. They list their modifiers under their health bar. Did you happen to notice what modifiers it had? Maybe it had Proximal Tangibility, which only allows you to hit it up close?

Ouch. Thanks. Layer 8