Just for testing, but I can upgrade to 6.2.4 in one of my J4125 baremetal NAS and I can login without problems (latest redpill bootloader with uefi).
But when I try to upgrade to 7.0, I have the same problem as @maxhartung I tried sataportmap with same results:
Tried: DiskIdxMap=00 SataPortMap=4 -> We have detected errors on the hard drives 1,3,4
Tried: DiskIdxMap=00 SataPortMap=3 -> We have detected errors on the hard drives 1,3
Tried: DiskIdxMap=00 SataPortMap=2 -> We have detected errors on the hard drives 1
Tried: DiskIdxMap=00 SataPortMap=1 -> No drives detected
Tried: DiskIdxMap=00 SataPortMap=0 -> not loading/no network
Tried: DiskIdxMap=00 SataPortMap=1 SasIdxMap=0 -> No drives detected
Tried: DiskIdxMap=00 SataPortMap=2 SasIdxMap=0 -> We have detected errors on the hard drives 1
Tried: DiskIdxMap=01 SataPortMap=1 -> No drives detected
Tried: DiskIdxMap=01 SataPortMap=2 -> We have detected errors on the hard drives 2
The motherboard have 2 SATA port, I added 2 PCI-e 4 Port sata (total= 10 sata port) that works fine with 6.2.4...