Hard Disk errors on system boot

[JonTTTT]

Pretty much every time I start my desktop PC, during POST, I get the blue "Hard Disk error (3F?)", run system diagnostics.

Running full HDD and memory tests shows no faults.

I have 3 HDDs installed. When I remove 2, I still get the error.

Things I have tried, all which produce the same error:

 - Connecting just the first HDD to the system, and leaving the other 2 disconnected
 - Connecting each of the other 2 HDDs one at a time, so only 1 HDD is connected at any one time
 - Moving the SATA data cable to a different SATA port on the motherboard (when I do this, the 3F? drive number changes to match the SATA port used)
 - Trying different SATA cables
 - Using different SATA power cables

When I boot with no HDDs connected (just my optical drive), it boots OK and lets me know it cant find a bootable disk.

Does it sound like I have an issue with my motherboard. It is a great MB but 2 years old and out of warranty.

Any suggestions will be appreciated.

[JonTTTT]

I forgot to mention in my original post.

The 3 HDDs:  1 is an SSD, and the other 2 are Seagate 6TB Ironwolf drives. 

I cannot get the error to happen when I only have the SSD connected.  The error happens almost every time when I have either one of the Seagate 6TB drives connected.