EX4100 drive failed

Hello, I have EX4100 (4*4TB) with RAID10. Drives 1 and 4 showed red lights; disc status was bad for both. I’d decided to replace both with equal ones. Started with the drive#4 - now I still have red lights for #1 and #4 (already new) drives. For drive#1 status is bad, for drive#4 is good and full test shows the following report:

Disk1 Failed - Full disk test failed. Please backup your data and replace this disk. If you need further assistance, contact WD Support.
Disk2 Passed - Full disk test completed successfully.
Disk3 Passed - Full disk test completed successfully.
Disk4 Passed - Full disk test completed successfully.

Nevertheless in notifications I see:
The drive 1 self-check failed. Contact WD Support.
The drive 4 self-check failed. Contact WD Support.

What’s wrong with drive 4 and what should be next step?

Auto-Rebuild has been always set to “On”