Art most but all not electric PTOs do occasionally need the air gap adjusted for wear. I would try that first. I not sure on your model but most should have about .018" gap with the PTO cold and the feeler gauge between the disc and the plate that engages it. There should be 3 adjustment bolts to to change this. A call to your JD dealer should be able to confirm that it is adjustable and the correct gap. Basically what is happening now is you are or are not sliding the PTO clutch enough. I would say your battery is a bit suspect and I believe JD recommends you engage at full RPMs. Welcome to WFM. Roger