Star Capella Regen going out/ shuddering

[nonomac4]

I recently bought a Star EV Capella. I drive it nearly every day, so it has almost 3500 miles on the odo. I have replaced the rear end because of a brake squeak that could not be fixed, which happened at about 500 miles. Now the cart is losing regen suddenly when going down hills coming off of a full charge. This is scary with the terrible brakes it has and my neighborhood has very steep hills. Does anyone know how I can fix this? Also, my cart has a Curtis controller and we turned the cart up so it goes about 28 mph. When I hit this speed sometimes it will shudder violently or sometimes it will shudder when I put the parking brake on and get worse until I shut off the cart. Unacceptable for a brand new cart, should have gone with the big three 😔