Please check if your monitor supports both PAL and NTSC modes, as it might be that it is booting in a different mode by default with the newer bitstream, and MEGA MAZE when it finishes loading may be again changing the video mode. It sounds like MEGA MAZE is in NTSC from the music speed, and I think newer MEGA65 bitstreams start in PAL.
Are you using an HDMI or VGA connection to the monitor?
Thanks Paul. I'll try to find out if my monitor supports PAL. It's a cheap Acer 1080p I picked up years ago, so I doubt it. I'm using HDMI for the input.
With that said, the monitor works fine when the Mega 65 is set to PAL or NTSC via the Freezer menu.
Do you know why the red light would be constantly on when using the updated COR?