ToME: the Tales of Maj'Eyal

I originally cleared Spellblaze before going to Dreadfell. I killed the Grand Corruptor, and Ssasshhiy'K in Spellblaze 1. I left a Damp Cave behind in Spellblaze 2, because it was too high level at the time.

I cleared that Damp Cave after Dreadfell, and now all of Spellblaze 2 has been repopulated including fog of war. The Ssasshhiy'K's event had also reset on Spellblaze 1, so I was able to kill her again. The rest of Spellblaze 1 did not respawn.

Important question: Are you running the steam version, and if so, do you have steam cloud saves enabled? They have a tendency to screw with stuff like this. If not, that's quite the odd bug.

No, its not an odd bug.
Offshoot dungeons have been doing that since they were added.

This is the GOG version. I do have an account set up to save to the server.