If you add this to the source, it might fix the graphic glitch on M3.
Fix by qw3rty
The M3 boot-menu seems to leave traces in the VRAM and Sprites-VRAM.
Setting the complete VRAM to 0 seems to eliminate the problem.
Include following code right after setting the VRAM-Banks:
for (i = 0; i < (131072/4 * 4); i++)
{
BG_GFX[i] = 0;
}