Do the 3 games have anything in common like all the maskrom chips being of the same make?
I guess you have already googled the CRC in case it's just a variant not present in my database?
I do know that Pokemon Stadium only dumps correctly with 3.3V and gives errors with 5V, never found out why though.
I also made the experience that N64 games don't dump correctly if one of the on/off or voltage switches has a resistance higher than 0.6 Ohm or something like that.
I'll probably have to adjust the timing in the code somewhat to make those edge cases dump correctly.