OOZNest Xpro V3: getting repeating lines of question marks

My 1500x1500 OOZnest has been working great for the past 6 months. Today, a weird little gremlin popped up on my Universal Gcode Sender screen. When I open up the command window, I get many lines of non-stop, repeating question marks. I've tried rebooting the software, rebooting the computer, disconnecting and reconnecting the USB cable from the computer to the Xpro board, resetting the commands and re-entering all the settings as indicated in the OOZnest manual. I also dumped the UGS and reloaded it on my computer but I still get the repeating lines of question marks. They stop repeating as soon as I close the commands tab on UGS.

I opened up the machine controls tab and entered 10 mm x,y, and z movements and they seem to operate the gantry controls properly, but I'm hesitant to to any cutting with this gremlin lurking around in my machine. I've attached a screen capture. Any suggestions would be great appreciated.