Posting from archive as previously not subscribed. I have a qnap ts-219p (kirkwood) in pieces at the moment as it is failing to boot the 4.2 kernel from a brand new install of stretch. I am also seeing problems with the sata controller interacting with the mtdblock driver I am going to see if rolling back a version or 2 of the kernel will work tomorrow and will feedback to the list. Regards Iain