I have a 2010 Toro MX5480 I’ve got an issue with. The belt recently shredded, so I went to the dealer and bought a replacement and got it installed with no problem. This seemed to create a new issue in which any kind of resistance while the blades are turned on quickly slows the blades down to a nearly total stop. The engine on the mower continues to run at the same constant speed and does not die out at all, just the blades slow down. What in the world is going on?