Problems with NAND reball iPad – Waiting for ipad on restore

Hey guys I have bunch of dead ipad boards and working icloud boards. Im trying to swap NAND. Im having hard time to have reballed nand to work. When restoring in hangs at the begging "waiting for ipad". I got one to work, which was satisfying.

I know rebaling is a mater of practice, I can remove chips without damaging pads and lifting surrounding components. The reball process it self i believe is perfect (nice even balls). So I think the last thing is to have it solder properly to the board. any tips how to get that part properly or what could cause this issue?

Reballed NAND

Thank you for any suggestions! 😎