DIAGNOSIS The soundbar's Bluetooth circuit is being triggered by a nearby device, like a neighbor's phone or your own laptop searching for devices.
FIX Disable Bluetooth auto-wake. Press and hold the 'Bluetooth' button on the soundbar's remote for 5 seconds. You will hear a confirmation tone. This prevents the soundbar from automatically switching to Bluetooth when it detects a pairing request.
IF THAT DIDN'T WORK Clear all paired Bluetooth devices. In the JBL One app, go to Bluetooth settings and 'Forget All Devices'. Then re-pair only the device you use.
HEADS UP If the input still changes randomly, the front panel control board may have a stuck or shorted 'Source' button membrane. This requires internal inspection.