MiSTer FPGA Forum

Normally you get a black screen when starting the core and then when loading a rom the Uni-Bios screen shows up followed by the game.
If you first use the NeoGeo arcade core from Blackwine and after that load the console core, without using any other core in between, the core seems to try to execute what is in memory: first a garbled Uni-Bios scren is shown and after that you can either barely see the game used previously in the arcade core or get an exception.
Loading a rom will proceed as normal after that.
If you use a different core between the arcade and console version everything works as it should.

Seems similar or identical to what I reported here:

viewtopic.php?f=29&t=3105

Yep! Exact same thing. I think it is a different problem as what was said in the comments you got. There is no need to reboot anything, just going into the OSD to load a rom and everything works fine. It systematically happens if the NeoGeo arcade has been run immediately before, it can either throw an exception or you can barely discern the previous game: no color, looks like a black cat in the dark, it seems to be kind of running as things move, I even saw Game Over appear after a while. It does not happen if you load another core in between the arcade and the console, at least with loading NES. It looks like the core wants to execute what is in memory before even loading a rom.