So I got into repairing this yesterday and here's what I found.
On the lower left side, behind the sheet metal under the steering wheel is some linkage that goes into a spring loaded tube. This appears to be what centers the HTS pedal. The adjustment jam nut was loose so I figure it moved. With the tractor running, in gear, adjusting this would make the tractor go forewords or reverse. I adjusted this so the tractor wouldn't move without pushing the pedal. After several attempts I got it so it would not move on it's own without pressing the pedal in one direction or the other.
I also noticed that the pedal had no spring when released when pushing the pedal foreword. It did have some spring when releasing after going in reverse. This spring action is apparently provided by a gas filled piston known as a "Damper". I replaced this at a cost of $145!! The tractor now works as it should.