Hmm, well if you are checking the specific plots with plot check and they pass, then all is good?
I guess although there is always this unsettling feeling that something is wrong. I’m at 4000 plots and no new chia in last 14 days 
I got this error on my plots that were previously fine after I copied them to a new directory over on the full node.
This was when the plot was still assigned to the old location where they had been just fine.
Once I moved the directory to the new location they all work great.
So I gotta think it is some kind of drive failure on the old location and I got them moved just in time.
What was your weird way of copying that got you this error?
Oh, it was a weird web-based NAS web GUI that copied all the files in parallel. Long story… so if you selected 50 files it would copy all 50 at once, simultaneously, rather than copying one by one.