If you update your RM4200D to the Series 52 firmware generation, it is necessary to exchange the Communication Controller. Instead of the RM420-850, you need an RM420-852/853 controller module. If your console contains a TFT display, you need to rewire it after the controller exchange.
The following diagram shows the conventional wiring of the TFT screen of an RM4200D console equipped with an RM420-850 Communication Controller.
After the update to the Series 52 firmware generation, the TFT display must be connected to the Communication Controller module in the following way.
Click on the diagram to enlarge it.