Characer Goes Limp at Bosses

Hi, I just wanted to share that twice now my character has "gone limp" i.e. I've lost control of them in some way when I get to a boss of a map, usually the delirium is in effect and there are mobs on the actual boss platform. The first time this happened was during the map with the Act 4 samurai, where he is at the end of the platform, as soon as I entered the platform my character could not attack and was stuck in walk, and all the mobs were attacking me and I was able to activate the boss but died before I could fight, then when I respawned I could just enter the arena and fight. Then the 2nd time I noticed, I entered arena with the bone skeleton guy from Act 2 in the middle hole of the arena (spins, fire, falls over, etc) and again it was delirious with mobs on the platform and as soon as the boss engaged my character entered a walking only motion and went into the corner and gets 1 shot. Not sure if this is my own doing or someone else has experienced this just wanted to share.