That was the next step, I'm rerunning a clear before that to see if it was a fluck or if it consistently fails on just one write.
Edit: Exact same result, 2MB not written or failed, can't tell. I won't upload the log, it's identical to the previous one.
I wonder if it might be an "off by 1" kind of error somewhere in the math, 2MB is the value of the sb parameter of dd, it might be used somewhere else.
Edit: Memtest done no errors... I'm stumped
Edit: Finally caught what I was looking for, I edited the script so the -t option would run over 1TB and I monitored dd_output, I got this amongst the normal output:
dd: warning: partial read (1126400 bytes); suggest iflag=fullblock
Added the flag inside the function write_disk(), clearing and praying (already past the point where the message was showing up).