D5-300C - One is not like the others

[Tangeloor]

I have three D5-300C's that have been running happily for months. All of these units are set to SINGLE and all bays are occupied.
I had some odd, but what I thought would have been normal behavior on one unit.
When plugged in and powered up, if there wasn't any activity, the drive lights would shut off until a drive would be accessed.
When the drive was called for by the computer - the light would come on and it would spin up.
My other two units - the lights remain on at all times the units are on.

On this one, differing unit, I have recently lost access to drive bays 1 and 2 The bays just don't show up under Windows 10 Pro. On this unit, these are the two drives that COULD be set for RAID, but I choose not to do so. All three units are set the same.

Is anyone aware of any oddities or revisions to these units that would explain this? Any ideas on the fix?