TLDR: I have the 4 gems but putting any or all of them in the altar does nothing,
I can't call the other platform and so I can't head down to the lower level and progress the story.
Any solutions, workarounds, suggestions what I'm doing wrong would be much appreciated.
---
I got the 4 gems before heading to the platform.
I put the gems into the altar and couldn't get any further. I was confused because Shadowheart has a voice line to the effect of "we have all the gems now so let's continue" so it didn't seem like I was missing anything.
I read about the bug where you put too many gems in the altar so you won't have enough for the second lock. That doesn't seem to fit my problem as I can't get past the first lock.
I went back to various earlier saves before eventually going back to one from before entered the temple to make sure I hadn't messed something up.
Before I've done anything the altar already has 2 gems in it instead of the correct 1.
The extra gem is interactive but doesn't do anything. When I insert the first gem from my inventory nothing changes visually but the interactive gem is no longer clickable.
The lift won't move. The traversal gem by the pedestal can be clicked but doesn't do anything. I can jump over to the other platform and click the gems there, but they don't do anything either.
Even as an elf monk with flying potions, + move speed equipment, potions of speed and vaulting etc. I can't seem to reach the lower level.
This is my second playthrough, wasn't an issue first time.
I'd love to find out I've forgotten something, or solve the issue using the gift of console.