The Original Prusa MK3.5 is showing the message: "Overcurrent detected on nozzle heater".
Error name: Nozzle Heater Overcurrent
Error code: #23308 (MK3.5)
The error is shown when there is a damaged cable on the hotend heater or any of its connections.
The most likely cause of this issue is damage to the hotend heater cable. With the printer cold and off, check the path between the hotend heater and the hotend heater block, and see if there are any parts that are visibly broken or pinched, or if the positioning of the component appears wrong, or different than the below picture.
Check if there might be an overtightened zip tie on the hotend cable bundle, on the rear of the print head.
In case there is no damage, check the cable connection to the xBuddy board. Try reconnecting the connector.
In rare cases, this error message can be shown in case of damage to the xBuddy board. If the cables and connectors are intact, try checking the board for any damage.