Trialmaster - frozen midfight, had to leave

So we were fightning the Trialmaster in a party of 2 - I died early, but continued to watch the fight. Approximately in the middle of the fight, when Trialmaster shouted "Entropy", my teammate became frozen - but Trialmaster froze too, and nothing happened. I tried to resurrect (to see if it helps), but my teammate was still frozen. After cca 2 minutes he had to leave because nothing was happening.

Hello.

This also happened to me. I entered alone and on the 2nd freeze he casted the first ball and then screen kept freezed. After 2 min I left but this actually felt bad as fragments were lost and rewards as well.
In terms of what could have caused the bug, at the moment he froze I was to get stuned by a heart.. either that or I was too close to the border of the arena and that caused the bug.
Hope this helps.