I don't use RPG Maker so I may be wrong here. But they set their tile sizes to 48x48 right? These are set to 32x32 and wont scale up to 48 properly.
I would try finding a plugin that allows you to change your tiles sizes! Looking on the forums I found these:
https://forums.rpgmakerweb.com/index.php?threads/change-tile-size.46748/
or this:
https://forums.rpgmakerweb.com/index.php?threads/tiled-plugin-version-1-3-0-released.50752/
Like I said I'm not familiar with RPG Maker but I think it's a little strange you can't change your tile sizes.