I am baffled at my copam cutter. It makes a knocking noise when the carriage brings down the blade, which it has never done before. I tried plotting with a pen and it worked great and made no noise. It also won't cut at all uness it is on the lower pressure settings, which makes no sense at all. When I put it on the lowest pressure it will cut, but it skips spots in letters, like it doesn't completely come back to cut where it started (that's plain as mud ) When I up the pressure it starts out great, but after cutting a bit it is only barely marking the vinyl. Checked the cutting strip and it has no cuts. So, not sure what to replace.... the mother board, the carriage, the blade holder???