New vinyl cutter failing-> experienced advice needed

Hello.

This incredible forum has made my first few months of vinyl cutting straight forward and thoroughly enjoyable; thank you all!

However, I have suddenly encountered a problem with my vinyl cutter and am not sure if I can fix it on my own...

Basically the cutter will no longer cut curves with any accuracy. It will cut straight lines along the X and Y axis fine, but suddenly cannot even draw the TEST CUT programmed into the machine because it contains a Circle bi-sected by an X. I have been using a plotter pen to test as was suggested.

I may be totally wrong, but, I have determined that it is not a problem with the cutting software, usb-to-serial connection or cutting blade, angle, speed or pressure. I have also oiled the carriage and the rollers that feed the material forward.

The cutter is a REDSAIL 1360, 50" machine I got brand new about 6 months ago as a low-end first cutter. I have used it regularly and without many problems since. I wonder if I have just blown a cheaper machine out of whack with heavy use or if there is something I am not considering as a total newbie(?)

Any advice would be greatly appreciated!

If it was a weekday, I would be on the phone with the dealer or cutting the jobs I have due on his "floor model", but instead I am desperately reaching out to you.

Thanks for reading.