Was having trouble with blade completing cuts for letters, leaving a tiny gap which created weeding problems/tears. Decided to change blade, although it was just a few weeks old, and now it won't cut at all. The knife housing goes up and down and moves as it should, but the blade does not engage at all. The blade is set to correct height, the offset is set to .25 for 45 degree blade. (tried several blades as well). I have cleaned the blade housing. Could it be coincidental that the blade housing needs replacement at exact time of blade change. I have the US Cutter LP-801.