As I type, I seem to be stuck in an infinite loop with Enfys Nest against Treya in phase 4. Treya is at 50 stacks and is attacking over and over and over and over and Nest just keeps flashing up the ...
There's technically nothing to fix, all the abilities are doing what they are supposed to. That said, the AHQ team said the Dev team are looking at ways to improve things when players get stuck in this loop.
You used a toon with stacking protection against an extremely fast raid boss with TMR.
Same thing happens with damage immunity on Jango or from Rey's lead.