Boot up sequence of MacBook stalling

I'm running into a peculiar situation with booting my MacBook Pro. Configuration is Sierra, 2TB disk, 16gig RAM.

When booting the Mac, I get the boot chord. the Apple screen and the progress bar. The progress bar will progress up to a certain point (usually 1/2 way; will go all the way to the end if I wait long enough) then the boot will stall out. I have put swapped different disk drives into the machine with the same results. I have also reformatted the drive and have appeared to have successfully installed Sierra, however the machine stalls out in the same fashion even after the OS is reinstalled. I have been able to successfully boot the machine from an external drive on a USB port so the processor & memory appear to be operational. I just replaced the drive cable for the hard drive so I have tried both new drive & new cable but still have the same stalling. I tried a Verbose boot and there was one message that appeared on the screen in the boot up that I had never seen before:

spaceman_free_completed:3138 sfq 1 error removing entry 2510331 from free queue: 2

This same message is repeated numerous times on the terminal screen (60-70 times) before it goes back to the Apple logo & progress bar display (and stalling). My suspicion at this point is that this is some type of hardware error in the disk IO system for the drive since I have replaced everything up to the connection on the motherboard and can successfully boot off of the USB port. Wanted to see if anyone else has ever seen any behavior like this and can provide insight as to possible options to clear it (short of performing a motherboard-ectomy on the machine).

Thanks for the help,

RichP