Assertion fail crash early in Jurassic Depths

Verification builds: Release 853103
Summary: Jurassic Depths crashes early on due to an assertion fail. This crash does not occur in earlier builds (e.g. 809752).

Repro Steps:
1. Download and start Jurassic Depths
2. Wait for dialogue, then the prompt to follow Peter Montgomery
3. Follow him to the entrance of the cave, where he will stop
4. Wait for some dialogue
5. Crash occurs very shortly following Peter moving into the cave
All in all, this takes less than two minutes.

Observed Results: Assert Failure:

Expected Results: No crash.

Screenshots/Videos attached: Screenshot of assertion fail message, as well as debug log.

Notes: From TRS: I have a theory. At that moment (I believe) we do /fill air to a bunch of nearby redstone underground to the right (this was a precaution from phantom redstone days). I suspect it might be triggered by that.