Forgemaster stuck in walking phase

Bug Report ID: #880183283

An Essence spawned on the path of the Forgemaster. I thought I'd just go back for it after killing him but he got stuck on it so I had to open the Essence. Afterwards the boss was stuck in the walking phase and didn't even create the lava waves. Even after stunning him, he just kept walking at me saying he will destroy me or someting but never did anything.