I have opened a game of NES and well; I exit and enter another game of NES and see a black screen but listen to the audio of the game.
Same problem to me.
set videomode to default in recalbox.conf (you should find some other post about black screen)
Work fine on my Raspberry Pi 3 (Batocera 5.8 Stable)
Change this line:
global.videomode=CEA 4 HDMI