I had a problem with the PTO staying engauged on my LT1050 a few years ago. Replaced relay located under hood on right side near oil dip stick. When problem persisted, and after more investigating, I found a scrubed wire to be the cause. Look at right side of transaxle, at the bracket your foot pedal linkage is attached to...the wire there grounds out your PTO (shuts it off), when changing to reverse, if ignition switch is not in the right position. In my case, the scrubed wire was grounding me out while going forward, or preventing me from engaugement at all. Disconnected it, taped it up, left it disconnected.....problem solved.
Had my seat and fenders off, for transmission oil change when this fix was done... Sure if you lay on the ground and look in that area with a light you will see the wire I mentioned....might be easier with deck removed.....Good luck, Bob