Acrobat Kid (J) graphical issue GBA

[gadesx]

I tried the japanese version of Aero the acrobat "Acrobat Kid (J)"
with mGBA 0.5.2 and latest nightly 0.6-4531-29d1da6 (Windows)

Just in title screen, pressing start appear a black line flashing.
Checking tools > Game log says:
"[GAME ERROR] GBA I/O: Read from write-only I/O register: 0DC"

[JMC47]

Confirmed, latest nightly as of today, Windows 10.

[endrift]

This appears to be caused by one of the two backgrounds it flips between (which are in theory identical) having a small region of the background blacked out. This causes the flicker.

I haven't yet tracked down why one of them has that line blacked out.

[endrift]

This happens because a VRAM DMA into OBJ RAM overflows (goes past 0x06018000) and wraps back around into the mirrored extension of BG RAM (0x06010000+). Will need to do hardware tests to see what the right behavior here is.