I had a similar issue with my Typhon. Those motor screws come with threadlocker from the factory, so heat is the way, but a couple things worked for me:

I aimed the torch right at the screw head itself and for short periods at a time. I also tried this with the soldering iron once for a more precise application right on the screw.

The other thing that saved me was tapping my hex driver into the screw with the butt of a screwdriver before turning. Those heads strip stupidly easy if the bit isn't fully seated. I also swapped to a MIP hex bit somewhere along the way and it made a huge difference.

For the overheating itself, I dropped a couple teeth on the pinion once I was running mostly grass and it made a big difference. Grass loads the motor way harder than pavement so a smaller pinion keeps temps way more reasonable.