I took my vacuum apart to clean the gunk behind the rollers, I couldn't get the pedal off as instructed by the link below. I just forced it open to clean it and now, after putting it back together (never did get the pedal off) the vacuum won't stay upright and it takes a lot of force to push while vacuuming, I think the two wheels are jammed and the pedal is not seating properly. I'm going to have to get rid of my gunk- making dogs ...HELP!! Here are the instructions for what seems like an easy task..