DIAGNOSIS The rail drive carriage is dry or the J-bar that connects to the door is binding. The StealthDrive is a belt system, so metal grinding points to the carriage trolley.
FIX Disconnect the opener from the door by pulling the red emergency release cord. Manually operate the door. If it's smooth, the problem is on the opener. Inspect the black carriage that moves on the rail. Look for worn plastic glide blocks. Apply a light coat of white lithium grease (not WD-40) to the rail where the carriage moves. Also grease the screw drive inside the carriage.
IF THAT DIDN'T WORK The motor gearbox could be failing, but this is less common. With the door disconnected, run the opener. If the grinding persists from the motor head, the gear assembly is likely worn.
HEADS UP Never grease the belt itself. It will attract dust and degrade. If the carriage glide blocks are cracked or missing, replace the entire carriage assembly (Genie part # 30841T) to prevent derailment.