Larian put out one patch to prevent spawning puppets from entering a suicide loop in crypt near endgame..that fixed most of the issues, but I found one variation that still caused loop.
When last puppet dies via means other than source vampirism, if there is a player near its respawn point with Opportunist ability and high weapon damage, the puppet will try to move, die to opportunist (ending combat) then respawn (restarting combat and refreshing opportunist ability). So it moves again and dies again in endless loop.
Each time it spawns, it has the first move, so my other character cannot do anything to break the loop..no chance to move away, unequip weapon, etc...I could only break loop by restoring an old save game. Easily fixed if the last puppet randomizes which spawn point it appears at (and hopefully doesn't still try to run past my melee).