Very odd sad iPod issue.

Hi, I have a 30GB iPod Video 5th gen 5.5 model with the search option.

It has the sad ipod screen but if I reset it with menu & select buttons it will boot & work fine, but if I reset it again it’ll get the sad ipod again. I have restored it multiple times & usually get sad ipod after the restore also but if I reset it it will boot and work fine again.

I have tried a known good HDD & HDD cable with no difference so far.

What else could I try? I can’t find any similar issue online. Thanks