Viper Napuatzi boss fight - wasn't able to move, then immune

I just got a bug where I became unable to move during the Viper Napuatzi fight, and after I paused and unpaused I was immune from damage. After killing the boss I was able to move again, though some of the adds/soldiers were frozen in place.

https://www.youtube.com/watch?v=eVh6tamNgqU

I *think* I was also unable to cast flame wall, I was trying but it wasn't casting though I was able to cast Spark.