I mowed half my yard this morning with now issues. I took a break for lunch. When I came back to continue, the blades will not engage. I adjusted the front bar for the deck to adjust the tension in the belt. This allowed the blades to engage when set at 4" deck height down to just above 3". If I go lower than 3" the blades don't engage any longer. This is a new mower with less than 10 hours on it. I cannot figure out why it would just stop after working fine this morning.