It appears that the way Google’s AMP error report in the Google Search Console is going to be scanning for AMP errors differently from the way it was done in the past. What this means is that some people who have deployed AMP for their sites may see a new vertical “update” line on the AMP error report specifically on September 19, 2016.
This update line means that Google changes how the report is working. This means people will probably see an increase or decrease in errors. This is a change in the way Google is scanning for errors in this report.
There was a page written by Google on data anomalies that says “you might see a fluctuation in your AMP data, due to a change in our scanning process.” There was a tweet by John Mueller saying that this has no ranking or indexing impact, and that it’s just a reporting change in the Google Search Console AMP error report. John said, “It’s an internal change re which AMPs to include in that report; it doesn’t affect indexing/ranking.”
@rustybrick It’s an internal change re which AMPs to include in that report; it doesn’t affect indexing/ranking. Confusing timing, sorry :-/
— John Mueller (@JohnMu) September 21, 2016