My first guess would be to check the voltage on that LED you installed - maybe its drawing a higher
Voltage than LEDOCD is expecting

If it is only doing it when you first power on the game, you might just be right at the current limit of the fuse. There is a bit of additional current draw when you first turn it on to charge the capacitors, and that may be pushing you over the limit. When I tested your board, I noticed you had installed a 3A fuse, and that would be a lot for a game full of LEDs. My own games typically run about 1A, for comparison.

So, you could install a higher value of fuse. The board can handle more current. The downside, however, is that if you do have a short, the fuse will take longer to blow and possibly cause damage to the board.

The most common reasons I've seen for blown fuses are shorts under the playfield, which might just be a wire that sometimes makes contact, and in a few cases, LEDs that have a short inside them.

The idea you had to disconnect all the lamp boards, then add them one at a time should work well to narrow things down. If it is consistently blowing every time you turn it on, it shouldn't be too hard to find using that method. If it is only occasionally, that would be more difficult to track down.