Seems like there is a problem with the bluetooth Retro Reciever (RR) in 6 button mode with the M30 controller specifically in Mortal Kombat 1, all other 6 button games are fine.
The ABACABB code doesn't work in 6 button mode.
The C button is 'bugy' during gameplay too, but only in Mortal Kombat 1.
edit: Seems Model 2 is affect, but not Model1 of the Genesis.
Can anyone please test confirm?