iPod flash storage detected in disk mode but sad face error on boot

I just used a SD to CF adapter along with a 1.8” zif IDE adapter to flash mod my iPod 5th gen. After connecting it I got the sad face error message so I put it into disk mode and iTunes recognised it and I can restore it. I first tried on my windows machine to restore it and then I could access the whole 128GB sd card. However when restarting from disk mode the same error comes up on the iPod yet again. So I tried again on my Mac and I was able to restore it in disk mode but this time iTunes recognised the iPod whilst in disk mode and I am able to sync music to it. However, after restarting the same error icon still shows. So the storage does seem to be working but for some reason the iPod is refusing to use it, anybody any ideas?