I've been soak testing A5 in staging for the last few days, and I've seen 6 failures out of 26 runs. They are all down to "MciReadBlockData(): TIMEOUT! Response:0xA404012 Status:0x48" when trying to boot a test image. The only sensible way to fix this is to add a retry on booting the test image, so until that's done I don't think we can deploy it in production.