You may want to think about your lighting where you do your cutting and at your machine. And the ruler you are using. Is it easy to see the exact cutting line? Or is it hard to line up? Maybe you need to see if there's a ruler that has very clear lines that is easy to see and line up. Or one that grips well on the fabric without slipping and doesn't require as much pressure from you to hold it down. Sometimes our eyesight shifts, making it harder to see ruler lines and keep cuts consistent.