When I fought against Lagon, during the phase where you fight him on the top of the arena I stunned him with the node from Drain Life skill that stun targets after a few seconds of channeling. After being stunned Lagon did nothing until phase 2 started. When I came back to him, I stunned him again and he got stuck again. Not sure if it’s specificaly the stun from the node of Drain Life or ALL the stun mechanics though.
Maybe it could also be the fear from Drain Life ? Maybe both combined fear+stun ?
I think it’s the fear that’s breaking him (there was a bug report on that), as I’m stunning him on my Void Knight & it’s not breaking him to quite that extent.