Got the same issue here as mentioned above... black screen and power cycling needed. GoodNES ROM, CPU-04 NTSC NES w/ 47k resistor, 8 gig class 10 Transcend SDHC. And Gimmick! worked with the stock mapper before.
Edit: and same thing with Dynamite Batman. If it helps, device info displays OS ver. 11 (11.1 really), Bios ver. 5, Cpld ver. 2. Mapper 069 isn't even listed as supported in mapper info.