[ThePair]

If you have a backup Curve, my suggestion would be to utilize the backup, and develop a way to strap it down in transit. You could just screw a few eye bolts into the floor on both sides of the toilet, and run some nylon straps across the top before you close down. That should eliminate any bouncing the toilet experiences from off road/dirt road driving, and prevent a repeat event.

Certainly worth a try, as it's a lot cheaper & easier than replacing the whole unit with a cassette. If it doesn't work, you can always just remove the eye bolts as part of the de-installation later and you're no worse off for the attempt.

I don't go anywhere off-road, but if I did, this is precisely the type of mod I'd do to try to prevent what you've described.