Hey, sorry for leaving for a long time without explanation. I've had exams. I don't know when I can start working on Genesis again, I only have a two week holiday but it'll definitely be sometime then. I'll make a post on the team thread when I'm good to go.
Well I realized after I PMed you that I actually have a copy of the Genesis ROM so I checked and, lo and behold, I saw that the movement permission for those tiles was 0x10. Just change them to 0x14 and it should work fine.