My refine started doing the same thing until I realized that the carriage was out of it's track. I apologize if this was addressed in an earlier response, but make sure the two little wheels on the back of the carriage are set IN the "V" groove that they are supposed to be nested in.
Also, if the carriage and blade holder are not 90 degrees perpindicular to the vinyl surface, then you will get what I call "chatter", or wavy cuts, unclosed cuts, and chunks like I see in your photos.
Good luck.