I just purchased an HU775H walk behind mower. When I got it home the drive system would not move it when in grass. I returned it to the dealer and got a 2nd mower. Same problem. The grass height is not tall and it doesn't even work with the deck at its highest setting. Am I doing something wrong? This mower is supposed to work right out of the box and I'm about to take my 2nd one back. If I have to do that I'll purchase another brand.