Some things to try:
1 a new blade and adjust properly.
2 take the blade holder out and screw it apart, sometimes little bits of vinyl go up into where the blade is and under the cap.
3 while apart, lube the bearing in the blade holder
4 if you get little nicks/uncut bits at the start of a cut on round letters like "o's" it's usually blade offset is wrong.
5 replace cutting strip.