On the WMS bb1 platform, the reels, reel door lamp matrix, Extra Bet button, 8 segment LEDS are all connected to the SPN bus. That is what the "ethernet" cables are for. I will detail the way it all connects, I hope it is clear. The SPN bus works like a distributed network connected by a series of hubs. The door is one hub and the reel shelf is another hub. The originating connector is located on the backplane and it is the only "ethernet" cable plugged there. The colors and types of the "ethernet" cables may not match your color scheme, I detail them to make it easier to follow the connectivity scheme.
First, the picture of the door. You will note that there are 3 ethernet cables, this is the first spn hub. The grey one connects the reel door flashing lights to the LED display panel that has the 8 segment leds. Then there's one beige cable connecting the LED display panel to the lamp matrix controller. The other cable goes to the extra bet button, which you should trace to make sure it is not broken either.
Second, the picture of the lamp matrix controller. One cable (beige with boot) comes over from the door to this board that is on the left side of the wall of the cabinet next to reel 1. The other cable (grey no boot) goes out to the reel shelf, which is the second SPN hub.
Third, the bottom of the reel shelf has the cable coming in from the Lamp Matrix controller (grey no boot, though it appear beige on the photo, but it is grey), and the other one goes to the backplane (beige with boot). You have to make sure that there is no damage to any of the cables.
Fourth, the backplane. You can see the SPN cable plugged in coming over from the reel shelf.
The door open error clears when the you close the door and the slot has a chance to check the memory. Some errors prevent that event from happening until you clear it. I am thinking your LED issue is causing the machine to not go further into the boot process.