Interlude Holten Estate Boss Bug

The Interlude Boss encounter in the Holten Estate never started/commenced when I entered the area. Thane just sat at the piano while the Lady E just danced/spun continuously. Casting spells didn't fix the issue. Reentering the arena didn't fix the issue.

Bug Report ID: #3459386191

My fight started but after defeating the Thane the woman just keeps dancing and I cannot end the encounter.

I had entered the vaal ruins during the map, this might be what bugs the boss.
After opening a new instance and running the map again everything worked as intended.