So, that happened 2 times in zone with (now) 3 psi-bugs where enter to building with Newton is.
I just unstealthed near bug and ran back to east exit.
After 2 turns bug stopped to move toward my PC, and acted only after I attacked it - threw a knife at it, and didn't hit, so I guess it somhow lost its attack mode.
Is it for every psi-bu gs or just these local I dunno.
Maybe it that animation bug when PC could stuck in something (and drop out of stealth) caused that, if NPC can suffer it.