I have a 52" Advantage deck Scag walk behind, whenever I try to engage the blades the mower sounds like it tries to get them going but a belt doesn't catch or doesn't have enough power or something. It makes the initial sound of starting the blades, but then sounds like they just get shut off. Sometimes I have to pull the pto switch three or four times to get the blades to engage completely. This began happening recently while I was preforming a spring cleanup for a lady with a LOT of trash, sticks, rock, etc. in her yard, I'm sure I hit some but not anything to seriously damage the mower. I also have a bit of orange twine (from a straw bale) wrapped around the blade and spindles, but I don't think that would hurt anything. It couldn't be any safety switches or bad connections because the blade wouldn't begin to engage if there was a bad connection, right? Also, the belts are tight, maybe too tight, I don't have any tool to measure them, is there a way to tell by hand? Has anyone had this problem or know how to fix it? Any help would be greatly appreciated! Thanks and God Bless you all!