Hi,
I've had similar problems when trying to run an Amiga emulator. I've found the process of using the emulators somewhat clunky through RetroPi/EmulationStation.
A few pointers to try:
Use UAE4All instead of UEA4Arm as I've found UAE4All to load most games without a black screen. I usually use an A500 kick start.
Try another copy of the game, some Amiga ADF files have been cracked and don't work well. Look for some clean Amiga roms, they aren't so easy to find online.
I've struggled getting multi disk games to load reliably.
Another issue is mapping USB SNES joypad a real pain to do on UAE4Arm, just wouldn't like the mappings or save them. UAE4All seems to save the configuration with some luck.
Overall, my experience hasn't been that great using the Amiga emulator. Using the older defunked UAE4All frontend seems to be more reliable.
If anyone has anymore pointers and tips please share.