[Map] GLITCH WHILE INSERTING TILES !!!

I downloaded a tile set online and I tried to inset it, by watching YouTube vids, It came out good in advance map but when I tested the GBA, the whole map glitches. And corrupted my ROM (good thing I had backups) so can somebody explain it to me !!!

And also is it possible to expand a map (Expanding pallet town into a bigger area) , if yes can u tell me how ? Thanks

Without seeing the actual issue, the first part will be pretty difficult to answer properly.

As far as making maps bigger, it's possible if I recall correctly You just have to change the dimensions in one of the tabs of AMap. You'll of course have to repoint it to an offset with enough free space (which I think AMap has the option to do also).

You'll need to show us the "corruption" or "glitch tiles" before anyone can really help you.

Naw I figured out the map tiles glitch it was jus a problem with the palette mismatch, anyway thanks for the help in expanding maps.:)