Repairs Simplicity Regent 14HP Hydro Safety Switches

Simplicity Regent 14HP Hydro Model 1692593. In normal operation I have been able to shut off PTO operation, set the brake with the foot pedal and lock, and then leave the seat while the engine is still operating. Now, I can start tractor while sitting, but when i turn of the PTO and set the brake the engine cuts off when i leave the seat. I replaced the seat switch and connector but the problem continues. Looking that the electrical schematics I cannot see another switch that would be connected to the foot brake or the PTO switch to prevent operation. PTO does work fine in terms of operation. Its an annoying problem to not be able to leave the engine running as my battery has had trouble maintaining charge and i would like to address this issue before the battery. I hope someone can assist. Thank you, Rick