I leveled up normally.
I tested Burning by bugging Dr. Lash a bunch before and after Helldiver.
I thought at first it was Burning, but having found nothing, I decided to test Sophorara, since I knew she had a Freezing attack, and Thermal could plausibly be Burning or Freezing.
I noticed...
The square outside Implant Station lost it's description.
Also, room name is 'Implantation Station', but it's referred to as 'Implant Station'.
In Flash, the room description disappears after entering?
For your first bug, do you have a Hardlight Bodyplate in your inventory? Did you use a Save Editor or the Cheat Menu? Because it looks like you have an item that thinks it's both a Cybernetic Exoskeleton and a Hardlight Bodyplate at the same time.
For both bugs, I'd recommend deleting them...
I think Lunaraia's and Dynamonde's reports are two different bugs.
I've been able to reproduce Lunaraia's report (though much less often than 50-50). It seems to also print the wrong room text.
Deleting EVENT_WHORIZON_STATE might let you trigger it again.
Setting it to 2 should make the game think you completed it. (I think there might be another requirement.)