I don't think the NAND/SATA has confliction, as I have many customer has them in the design.
Does this issue only seen on one board, or it is universal issue? Ever tried to replace the Nand flash?
Try using other SATA devices, such as other HDD, flash drive, mulitplier etc.
It looks like the uboot is never impacted, is that true?
BR,
Eason