Mektul Forgemaster AI break

In the boss fight with Mektul, his AI can be broken by stacking stun and freeze. This will cause him to stop attacking and instead slowly walk towards the player. His new walk speed is slower than the approaching molten gold and cannot be attacked off screen.

Further information:
I managed to freeze Mektul first using +cold damage on items, and his stun threshold was crossed less than a second later from lightning arrow + lightning rod. This caused the two debuffs to expire at the same time, with freeze expiring first.
This happened as a level 44 deadeye ranger on act 3 normal.

Add my experience : Mektul broke when I stun him during his molten wave cast.

had the same experience during the normal playthrough
on hard, he just went back at the start of the map past mid-section. couldn't hit him anymore. he went back when i died to lava to taunt my corpse afterward