On the Original Prusa XL, communication with the peripheral boards (e.g. Dwarf board) is achieved using the MODBUS protocol. In MODBUS, there are two types of devices: the master and the slave, also known, respectively, as client and server. On Original Prusa XL firmware, the master is the XLBuddy, and each slave is called puppy.
If one of the puppies does not respond to a request from XLBuddy within a specified time period, the printer will show the message: "Waiting for puppies to start timed out".
Error name: Puppy run timeout
Error code: #17522
The error most likely indicates a disconnection or fault with a cable connected to a peripheral board, that happened during a printer operation.
Inspect the wiring between the Sandwich board and the indicated puppy board for a cable positioned into an incorrect port, a loose connection, or a visibly broken cable.
Download the firmware and if necessary the bootloader, and transfer it to your USB drive. Make sure to unmount the drive from your operating system before physically removing it.
Insert the USB drive back into the printer and reboot the printer using the reset button directly next to the knob to initiate the flashing procedure. In case the procedure does not start, reboot the printer again by pressing the same reset button, and while the printer is booting up, press once the rotating knob.