The Jade Islands / Eye of the Storm uncompleteable

Hey, just reporting a bug I ran into.

Steps I did for it to occur:
1. Map with delirium fog on via the mirror at the start.
2. Finish phase 1 of the boss fight
3. Boss does his role playing and runs to end fight area.
4. Kill delirium spawns in the corridor before the boss final area.
5. Boss phase 2 starts before you reach the area
-> red blob / border blocks access to the final area
-> boss jumps to corridor
6. boss goes down to some arbitrary hp, and last phase doesn't trigger, nor does he die or take anymore damage.
-> Boss cant die, map is un-finishable
7. Instance is destroyed
-> map is failed.

Br, KJ