Hello. First post, new to this sight. I just purchased (new to me) Sovereign model 1692798 garden tractor. When I got home I parked it in my garage and went inside and ate lunch. When I came back out to admire my new toy, I leaned against it and it rolled forward. I was under the impression that a hydro transmission would prevent the tractor from rolling unless the "transport" plate was pushed down to depress the "poppets" on the relief/dump valves on top of the hydro unit. The transport plate was up and the poppets on the valves were up. The hydro trans seems to work OK when mowing. It does slow down a bit going up hills and speed up going down hills so I have to move the control lever to compensate. Is this normal or something I should be concerned about? Any advise is appreciated. Thanks.