I have also tried to adjust the cable (not over tighting) with no luck. Do yourself a favor, go to Walmat or some other store and buy yourself a cheap self propelled mower or a good quality mower.. You will have less hassel and agravation plus save some money.
I have bought this same mower from Lowes 7 months ago. I am experiencing the same problems. I have the sent the mower to the shop once after 2 mowes it is doing the same thing. The mower boggs down in the slightest high grass and the underneath gets full even in dry grass. I have owned many mowers in the pass and have never had to tweak one out of the box. My evaluation is this mower is an expensive major piece of junk. Of course I am beyond the point of no return on getting my money back.