i have the razorcut38 and tried to raise the blades because the grass/weeds were so long, but i couldn't get them to adjust. now, when i first got the mower i needed to start with the blades higher, then moved to low once the lawn was shorter. i don't remember it being hard to adjust---the slides just---slid and moved the blades---easy! but now i can't get the mechanism to move at all. how do i move the mechanism?