Between Macrium and Acronis showing I/O errors or failing to validate, this has been the first evidence to me that a hard drive is about to fail several times. My experience in trying to repair the harddrives with software has always resulted in the hard drive failing soon after regardless. I would immediately replace the hard drive, and be sure of my backups, and data.
This is your answer. Most likely. Or, A defective RAM module. Yes, it sounds strange but it happens...
Can you post a screenshot of hdsentinel showing all the SMART values?Sometimes the overall result may be positive but some individual values may indicate some issue.