TI 2011 - Failed to read data from the disk

(This topic has been covered in some older posts for older Acronis products but I was unable to find a solution)
On backups of one specific disk, I receive the following error:
Information: Failed to read data from the disk.
Details: Failed to read from sector '379,143' of hard disk '3'.
Failed to read the snapshot. (0x10C45A)
CRC error (0x100155)
I ran the disk through CHKDSK M: /F and it pronounced the disk clean.
I ran the disk through CHKDSK M: /R and it found and replaced some bad clusters
I ran the disk through CHKDSK M: /R and AGAIN it found and replaced some additional bad clusters
I ran the disk through the manufacturer's diagnostics and they pronounced the disk healthy.
I ran the disk through the most thorough option of SPINRITE (it took five days!) which, supposedly, fixed everything.
I am currently running CHKDSK M: /R and it is, AGAIN finding and replacing some bad clusters.
Questions:
Why does CHKDSK find NO problems when run with the /F parameter but does find problems when run with /R?
How do I find out, with some degree of certainty, if this disk is still ok - (given that Spinrite, Hitachi's Drive Fitness Test, and CHKDSK /F pronounced it healthy)?
If it is not ok, how do I fix it (and get Acronis to produce a "clean" backup)?