I was mowing along as usual. I bumped the mower against a tree, not hard just bringing it to the ege, and suddenly I had a loss in power. The mower still cuts, it's just not at the same speed as before, which means the mulching functionality is pretty much lost. I've searched around quite a bit on this, and most people with this issue have a dirty oil filter. For me, I don't think that makes sense, why would a filter suddenly get dirty? Any ideas?