Unfortunately, the last two trimmers I have purchased (portable, inexpensive Fiskars and Cutterpede trimmers) warped or did something weird over time. I don't know what I would have done to make it happen, but it seems like the track warped and is no longer at a 90 degree angle with either the cut lines on the trimmer or the top/bottom edges of the trimmer, making it almost impossible to get a 90 degree cut. They were never perfect when new, but the problem got worse with age. I can't be the only one with this problem!