DIAGNOSIS: This is classic worn drive gear failure. The SilentMax uses a composite gear between the motor and the chain. Teeth strip under load (up), causing grinding.
FIX: The gear kit (Genie part #30224-TKV) must be replaced. Disconnect power. Remove the light lens cover to access the motor unit cover screws. Remove the cover. You'll see the large white nylon gear. Remove the old gear, clean old grease, pack new gear with included lubricant, and reassemble.
IF THAT DIDN'T WORK: If noise persists, the motor sprocket (the metal gear the nylon one meshes with) may also be worn. Inspect it for sharp or hooked teeth. Replace if damaged (part #30240A).
HEADS UP: Do not operate the opener with a grinding gear. It will destroy the sprocket and lead to a more expensive motor replacement. This is a common wear item every 5-10 years.