Google posted on the Search Console data anomalies page that they fixed a bug with the content mismatch errors report within the AMP, accelerated mobile pages, section. "We fixed a bug in counting content mismatch errors, therefore some users may see an increase in the number of AMP errors for their site," Google wrote. Google added you may now "see an increase, check your site for content mismatch errors."
Here is a screen shot of the report I see, notice the "Note" label which hyperlinks to this section on the data anomalies page:
So make sure to check out the report and fix any big content mismatch errors when you can. It does not seem to be a critical issue but just a heads up.
Forum discussion at Google+.
