Thanks, guys!

@cooba: That line was indeed missing from my JCS.ini file. I updated the event there. Fortunately, JCS allows you to immediately remove all events (or those of a specific kind) at once without having to do it one by one. After doing so I put new No Fire zones back, but only around the starting areas. With Set To on 2 I hit 'Save & Run', and I'm happy to report that it works.

If I can't think of any further improvements, I'll re-upload the level and hope to see it in action one day .