Had to go back and watch a replay to figure out what killed me after this. This happened after a prior bugged attempt.
First Lightless Arbor the usual bug of invisible walls in front of the entrance just after spending the key.
This time LA again, I couldn’t see any of the walls but party members could. Later in the dungeon my party members to different versions of the same map. We could no longer see each other, were both still in the dungeon though. Just different instances.
Then none of us could enter the boss room because it kept saying it was waiting for everyone else at the voting screen.
Eventually everyone except one person had to leave so that one person could do the dungeon (me). Then I died to this.
After this I tried Temporal Sanctum solo. I didn’t get far. There was no way into the dungeon after using my key. The light thing that indicates a travel point at the bottom of the stairs never happened for me.