DIAGNOSIS The printer is entering sleep mode due to an inactivity timeout setting. This interrupts the data stream.
FIX Disable the sleep timer via a hardware button sequence. Ensure the printer is on and idle. Press and hold the POWER button for 10 seconds until you see two quick green flashes. This toggles the sleep function. Confirm it is off by waiting 5 minutes; the LED should remain solid green, not blink slowly. Next, in your computer's power settings, disable USB selective suspend setting. For Bluetooth, ensure your phone/tablet is set to not optimize battery for your printing app.
IF THAT DIDN'T WORK RF interference is disrupting the Bluetooth signal. Maintain a clear line of sight within 3 meters. Move routers, microwaves, or cordless phone bases away from the printer and computer.
HEADS UP Printing large batch jobs via Bluetooth is inherently unreliable. For batches over 20 labels, use a direct USB connection.