Ok. I've seen this before. The reason is because GameEx changes the rom names from the rom name to the rom number for handling of this particular emulator. But the problem is that it also is looking for the numbered videos to match. This was a flaw in this particular setup which has been brought up before but was never addressed. Solutions would be to use GameEx's integration for this emulator, rename your videos to the numbered roms, or to not use the map file but use a loader for the handling of using the rom number in command-line.