Colossi Infection cave quest non-completable

This is the last cave I need to complete in order to start lootrunning. I ran it for the first time at lvl 89 (past the required lvl), and saw the blue/yellow xp chest animation, opened the chest, and got the 320k xp. This is usually enough to confirm the cave did in fact complete, but this one doesn't for some reason.

I've tried multiple times to go through, collect the mid and right chests, exit, and the "Progress" holo at the start never goes past 0. I'm not sure what I messed up, or if I'm missing something, or if I'm softlocked by a bug (since IIRC opening the XP chest always implies having completed the quest).

Thanks!