Yes it's a proper German MD1:
http://notaz.gp2x.de/img/hw/megadrive_model1.jpg
Note that I also have MegaCD + 32X attached, I know those have effect on open bus at least.
The purple screen is on a Mega Everdrive v1, consistently getting it every time on the same spot. I haven't seen any other problems caused by MED except my own tests that use STOP opcode - this causes MED's DRAM corruption because MED wants bus activity to work properly.
I've tested with another flashcart (raw flash, no SD card or any menus) and only getting black screen with that. I've checked and it runs other games fine.
EDIT: I've retried maybe 20 times with this flashcard and it worked 2 times to completion (2 green tiles), all other times just black screen. Maybe you're inadvertently using uninitialized RAM or some register?