You used base 56 for IOS249 and base 57 for IOS250? Did you try with both? Do you have base 58 on IOS251 (shouldn't be needed but some people still install it and it could help too I suppose?)
Base 56 should work with the vast majority of games, I am not sure about those two though.
It's also possible you could have bad/corrupted dumps, apparently WBFS corrupts existing games when you add new ones sometimes. I suggest doing an error check on your drive with Wii Backup Manager, and converting it to FAT32 with
http://gbatemp.net/threads/how-to-convert-from-wbfs-to-fat32-or-ntfs.292391/ and if none of that helps try replacing them with a clean dump.