I bought one based on this thread, but only set it up a few days ago.

Two days ago, my five-year-old requested that I print her a cat. I downloaded two cat models, one that was print-in-place bendy and one that was meant to test your calibration. I tried to print both, but both of them caused the printer to hang after displaying "stop processing, please wait … "

I spent several hours testing and troubleshooting this, only to find an old thread saying that the printer firmware can’t handle filenames between 6-9 characters (not including the extension), meaning the filenames could be 5 characters or fewer; or 10 or more. I had named my files calicat.gcode and flexicat.gcode. After adjusting them to be longer filenames, everything started working beautifully.

I’m very happy with the printer now that I know that, but it seems such a random error that it was very frustrating to try to fix. I thought my printer arrived broken. Hopefully if someone else encounters the same problem, they find this post and it fixes their problems!