Root Restore error after odin flashing back to stock rom

[chrisjv3393]

So I have a rooted prevail with a custom rom. I always go back n fourth from custom to stock but I always get a error in CWM when I try to restore my backed up stock rom. For example..

I back up my stock rom in cwm then flash a custom rom
But over time I get bored of the rom n I decide to return to stock by odin flashing it. Then I go into cwm to restore my backed up stock rom n then I get an error ..does anyone kno y this happends? Btw its FA19 stock rom for both my backup and odin image

 

[Koumajutsu]

you didn't convert /cache back to RFS when switching back to stock

 

[chrisjv3393]

I have no idea how to do that lol any help for future references? Lol