QNAP fails to reveal data corruption bug that affects all 4 NAS
"In short, if you have any QNAP running a version before 4.3.3.0154 20170413 or 4.2.5 20170413 then upgrade it immediately as you risk data loss should you have a drive in your RAID5/6 array fail. No amount of data scrubbing will recover the data if you have a disk failure and have not upgraded to these versions at a minimum."