At first report we had the customer connect the drives directly to the Areca RAID controller and everything worked. This narrowed the issue down to the backplane.
Now, I just received a call from another customer with the same issue. We mentioned that Norco switch his backplane and everything works flawlessly now. So it seems that some Norco backplanes have signal or other issues.
So if you have this issue, please contact Norco. This is not related to OS or controller because the drivers installed correctly. MRAID GUI is working properly with the controller detecting the missing drives and RAID array the way it’s designed in the event log.
Raid is meant for data redundancy. Always make a back up of your data!