Applicable if you do not use a separate LCD panel with the Me2, your printer has stopped mid print, or you have multiple printers connected to a single USB hub.
The Ultimaker board within the Me2 can provide power from both the USB and regulated from the 19V supply. Removing the "ARDU_PWR" jumper forces the brains of the Me2 printer to power directly from the USB only. For most setups it is fine to leave this on, however for setups which have multiple 3D printers running from one hub, or if the printer looses connection mid print it may be caused by voltage spikes when the Arduino is accepting power from both the USB and the internal voltage regulator.
After removing the jumper you will need to reboot the printer and reconnect.