This mower has been working fine until about a week ago, when it started to not respond to the steering wheel. Now it steers ok sometimes. Reverse steering seems to be ok. So I took off the rear frame cover to see if it was something simple. First thing I noticed after cleaning a lot of dried grass that was in every nook and cranny is that the two billows operate when in reverse, but not in forward. Since they work like the rocker on a rocking chair, it is hard to determine which one is not working. I would guess that one is for forward steering and one is reverse, but I do not have any idea which one. I feel the billows are ok since they do work in reverse. I appreciate any help. What should I look for?