I am experiencing the same issue as of my upgrade to WP v4.7 on December 12, 2016. For some reason amp link code is being generated on attachment pages (image pages.) For example, on attachment page https://blog.drpower.com/chipper-graphic/ the code <link rel=”amphtml” href=”https://blog.drpower.com/chipper-graphic/amp/”> is being generated by WP. This of course is kicking out large numbers of 404 errors in Google Search Console as each image in my media gallery is assigned an attachment page. As a workaround I may try a 404 redirect plugin until a patch or official workaround comes around.
