Running for an hour, oil heats up in transaxle, then stops moving, not good. Running for 15 minutes, oil heats up, stops moving, near the end of the transaxle usually. The pump and drive motor faces (where it sits) are probably scored. Requires replacing expensive parts, and still not guarantee.
This scenario is one of the many reasons most shops only offer remove and replace on hydro pumps, pump motors, and transaxle units. Too many variables and not enough profit, and potentially unknown hours of frustration and risk.