The Original Prusa XL can detect a power fault on the Modular Bed, with hardware measurements: in case this happens, the printer will show the message "Power failure".
Error name: Modular Bed Error
Error code: #17319
Inspect the modular bed for physical damage, such as scratches on any of the heatbed tiles surface.
Inspect the wiring between the Sandwich board and the Modular Bed for a loose connection, or a broken cable.