If your cutter is cutting poorly, there is uneven cutting depth, or incomplete cuts. Then you may need to replace the cutting strip on your cutter. To check your cutting strip remove the vinyl from your cutter. Run your finger along the cutting strip checking for deep grooves, scratches, gouges or tears.
The cutting strip would lift up from the surface and then it can be pulled off. Sometimes there is a layer of tape over the cutting strip and that can be removed as well. The new cutting strip should be able to be set into the groves where the original cutting strip had been located and there should be an adhesive already present inside of the groove for the cutting strip and then new strip can be placed into the groove, either side is fine.
You can purchase a replacement cutting strip by clicking on the link provided.