What is ASD ERROR - -33011 [Error locating BSD device in IORegistry]

I have a mid-2012 MacBook Pro that had the following symptoms:

1. Machine would not start - black screen, three beeps.

2. I removed the RAM (2 X 4GB sticks) and reinstalled one at a time in each slot - result: machine booted fine each time even with both sticks reinstalled.

3. Machine seemed sluggish, slow to boot, slow to finder, slow to open apps but was otherwise usable.

4. Machine was restarted several times without issue and also without much improvement to speed despite running Malwarebytes (found 18 things it quarantined) and Onyx. Disk Utility also found no problem with the HD.

5. After being on for about 12 hours I left the machine doing a copy to a USB drive. At some point the screen went black and the three beep pattern was playing.

6. I forced the machine to shut down and when I tried to power on, got the three beeps again.

7. I forced shutdown two more times and eventually it booted ( I did not do anything with the RAM).

8. I booted the machine with ASD 3S150 (the version for that machine) and ran the default test.

9. All tests passed until it got to the following hard drive test and the error stopped the test:

07/21/18 12:10:26] Hard Drive - Internal (test #5) - Check SMART status

- Check the SMART status of a device.

[12:10:27] ERROR - -33011 [Error locating BSD device in IORegistry] -- TEST FAILED

9. None of the memory tests produced an error. I am currently looping through memory tests and not getting any errors.

10. I ran 10 loops of the hard drive tests and Error 33011 showed each time.

Over the years I have replaced several hard drive cables in 2010, 2011, and 2012 MacBook Pros. In none of those cases was I getting the three beep error at startup or anytime. I was experiencing sluggish system performance or in some cases, unable to boot fully into the OS (crash/freeze).

Does anyone have any advice on what could be wrong with this machine? I do not have spare parts to test with and I'm not sure I want to order RAM, hard drive, or hard drive cable without some plausible advice first.

Thanks in advance.