Engine Walker mower 42" deck, lever engaged blades not pto switch PROBLEM! HELP!

Ok, I have owned this mower since 200 hours, it now have 640. My crew only uses it a few times per week to get into back yards with gated entry ways. The other day i was notified of this problem. Before I get into it i want to say this is a 42' deck, small walker with 13 hp kawasaki, it does NOT have a pto switch for blade engagement, it is engaged by a lever on the right side of the machine. This mower is approx year 2005. The mower starts right up and runs like a top, we maintain the hell out of our equipment but this is the only walker we own so we are not real educated on it.

Fires right up, runs great... you push the main drive lever forward and you hear the hydros spool up like normal but then you try and go forward and it moves some but "bogs" down or winds down and almost stops. Also when you are just sitting still with the engine running and engage the lever for the blades, the blades will not engage. This is not an electrical problem. It almost seems like there is something slowing (gears box)?? The belts are all new, pully bearings in good shape, nothing locked up that I could see.

Anyone have this issue before?? Any help would be greatly appreciated!!

I would check to see if the belt is routed outside a belt guide. Another check, would be to pull the spark plug (for safety) engage the PTO lever, and then turn the blades by hand while some one is watching for any binding.