Nemesis enemy defeated when portal spawns, no itherian boss battle or Umaro

Version: 0.20.2

I don’t know the exact order of events that happened, but here goes.

I was in an itherian realm.

I completed a quest which spawned a portal, and I believe at the same time entered a battle with a nemesis creature.

Upon defeating the nemesis creature I was given loot for it.
The strange part was I was taken inside the itherian portal, but the boss and Umaro were missing.

The chests could be looted though.

When exitting the portal I was taken back to the castle.