Faulty GRaid (with thunder bolt) Chassis or Drive?

Hello, I have a g-raid that I thought one of the 4TB drives went faulty in. So I replaced the set but I can’t get it to formatt properly using the configurator tool. I have mixed and matched the four drives and it would never foramt properly after using hardware raiding it.

Where I am now is if I have one drive in the bottom chassis that I format as one drive. When I turn off the drive and move that drive into the top slot it appears as a GPT partition split 2018GB and an unformatted 1678GB partition. Neither of these partitions can be formatted. If I move the drive back into the bottom slot it will appear as the correctly formatted drive.

So I formatted all the drives in the bottom slot (drive 1,2,3,4) but not matter what mix the top slot never appears formatted.

This would suggest a faulty chassis to me. But if I put 2x500GB drives in it it formats as expected. I am not really sure what to try next? Has anyone any suggestions?