Hello! I solve the problem with disk errors and disconnected sata ports by buying PCI-SATA card on Marvell 88SE9215 chip.
I think in my case my motherboard physicaly have 3,4,5,6 ports. And 1,2 ports are dummy
Maybe synology can be installed only on first sata. Or there are errors, because first sata does't exist
I didn't find solution, how to skip or disable or remap missing sata ports.
With sata card everything works fine