Hello !
It can be many things, let's start by trying the basics, it has worked for me on more than one occasion.
-You try with other games? do it
-Try moving or slightly passing the slot cartridge with the console running, it may be a bad contact due to too much pressure when inserting it or the other way around.
You can also see immediately if the image improves or remains the same.
-Do a good clean of game cart pins and board slot pins ( i use credit card under a 100% cotton shirt with alcohol on it ) you insert like a game in slot and that clean it a little )
-Try to press slightly with the game ON the big chips of the MVS board to se if the image is better ( maybe cold joints or without solder doing bad contact ).
Its important you try more games can be a problem of Mslug2, a cold solder joints maybe with reflow of some memory chips like P, M and C's...