gravely drive belt rejection

I have a Gravely HD ZTR that is eating $50 drive belts.  Unit has 200 hours. Fluids have been changed per manual recommendations,  First time, forward progress stopped the belt was severed and trailing out the back and i noticed a bit of oily residue on it.  Didn't thing much about it and put a new belt on following Gravely's  how to video.  btw, didn't notice anything big in terms of oily stuff when changing.  The unit ran for a couple hours and then spit the new belt.  Didn't break but was abraided with cord damage.  some oil or hydro fluid present again.  Don't know if it was the reason, but wondering if anybody has had similar issues and if so, most likely place to look for a hydro leak.  Not a major leak as both fill port reservoirs have 1/2 to 1 inch still in them.  New belt was checked after installation and all pullies were correctly engaged and seated before idler spring was reattached.