Google posted on the data anomalies page a new bug with their Google Search Console reporting, this time with the AMP reports. Google wrote that "Some users may see elevated levels of errors of the type "Major content mismatch" due to a processing error on our side." "Correct error counts should return to their actual levels within few days," Google added.
This would have happened between the dates of January 23, 2018 and February 3, 2018. Personally, I am not sure I see the "note" added to either the old or new Google Search Console AMP reports.
This is what I see, but that note is about an new error on January 26th, not the 23rd.
I checked a few more sites with AMP and not seeing the "note" - so maybe they didn't add the note yet to the reports?
Forum discussion at Google+.