POE2 Cannot enter boss arena in Grimhaven map

Reporting a bug where you cannot enter the boss arena in a map called Grimhaven
https://imgur.com/a/AY8uirr
As you can see only 1 enemy is remaining in the first image, the boss arena has some invisible barrier which doesnt let you walk in and there's no "portal" or floating text saying "Enter arena" so I'm not sure what to do but this map is unable to be completed.

Same here,what I should do?

same, this map is bugged