Yes LOL! Actually uneven terrain could do it too but I agree with the first guy: Bent or blades worn past critical (you'd be surprised the slivers I seen people still call blades), bad deck adjustment (check and double-check this REAL good) and it can also be a worn / broken / missing part on a deck (like one them cotter pins or hitch clips or the steel pins), low tires / air pressure and worn bearings / spindles. Also check the connection(s) between deck and frame, that could get loose where the bolts hook up AND I just realized: Your deck could be missing or have a really worn caster / deck wheel - Also check the bearings on all your riding wheels. Something is likely loose or worn beyond a certain point - Put your mower on a flat paved surface and take a good look around it all - See if you can see a sag or one side lower than the other. Last but not least IF you are bagging with a side-discharge, as the bag gets full of wet / rich heavy grass it will add weight to that one side - Empty bag more often. Good luck.