I'd be doing the same thing. Getting weights and a tach out and adjusting speeds on main valve and rupture valve. I had a car once for a year intermittently trapping folks early in the morning. But noone had details, just customer got them out. Car ran fine, I swapped alot of parts around with another car. Finally happens again and I talk to the folks trapped and they said it always happens when they're riding it down with the floor scrubber machine in it.... it was the main valve not being regulated going too fast, tripping rupture valve.