I have a 4 year old 1025R operating a 60D auto Connect Deck. While cutting grass a flapping type noise can be heard coming from the deck. I discovered the belt has been flapping so much it has created a black mark on the deck. I am about to change the belt ($86). The belt is not frayed or damaged in anyway. It appears to be too long now. The idler pulley spring looks good but it may be the culprit or it and the belt. Anyone had this problem? Thank you.