Sometimes 2 blades stuck together will do that. Also , you stated you flipped your mat over?? I have a mat that I never get good cuts if it is ( wrong side up) have you tried flipping it back over? Why did you flip it? If it has become rough a light ( sanding) will fix it right up. I use fine ( 100 grit) sand paper - or one of those green scrubbies work pretty good.