I posted this question up and then deleted it thinking I had solved it, but apparently there's more going on here, so I'm reposting it.
I completed Cauldron Iota tonight, but the map icon is still grayed out and shows "Unknown Cauldron (Completed)" as its icon tag. I tried running back over the door, but that apparently doesn't get Aloy close enough to trigger having "seen" the Cauldron for the map icon. https://imgur.com/K0UQkjn I went back to the alternate entrance and it's closed off, but while I was in the crevice, the map icon turned green and I assumed that meant it was fixed. However, after heading back out again, the map still shows it as unknown. I know it's minor but it's really frustrating. Does anyone know a ay to fix this properly?