Very helpful and could direct you where needed. Dont just go replacing parts without finding out what is causing the issue.
I replaced out a board because I needed to, but found out that the transformer was giving incorrect current and ruined the board. So if I just replaced the board without finding out why the board got messed up it would get expensive. There are numerous parts that power comes through before current makes contact with the board.
I'm sure you got your answer by now but for the benefit of others seeing your post, I will try to offer some information.
Service 52 was introduced with Index I (2016-09) units which now have LED lights in the door. The possible reasons by RATIONAL is to check the cable from A7 to A8. The A7 board is usually mounted near the top right hand when you are looking at the left side service access. The A8 is a board that was mounted inside the door. However, in later models this was replaced with a new harness that eliminates the A8 board for a more waterproof design.
If you have the A8 board, this can be retrofitted but you need to provide a serial number.
Besides the A8 board, the fault is usually at the door hinge. The LED harness runs through the door hinge and can be damaged if the door trip tray (table models) or hinge cover (floor models) is knocked out and it is now exposed. Pinching of this wire can now occur.
On stacked units, the top unit LED harness can get damaged as the operator removes and reinstalls the metal drip pan.
If this error is combined with a Service 34.X, you should also inspect the interior halogen bulb and socket. A short here goes back to the A7 board and can create either of the errors.
Check also for connections on the LED bars. Many operators keep the door open slightly which now allows heat from the interior cabinet to reach the LED's. Doing this is not a good idea even before the LED's were introduced. Either door should be closed or open completely to avoid unnecessary repairs. This can also cause the LED optics to become brittle and crack over time.