srcset not http in 4.7

Upgraded to WP 4.7 over the weekend among other code updates and today we are having the problem that the image “srcset” value contains http values instead of https on our https site and this is making only our blog post images not appear correctly (images in header and footer show up fine).

See this page for example:
https://www.ppumc.org/2016/advent-2016-prepare-heart-mind/

If I go into “Inspect Element” and change all srcset values to https then the image loads fine.

I have tried using SSL Insecure Content Fixer and your Force HTTPS srcset plugin and neither seem to be able to fix this for us.

I tried using all the different https detection methods and all modes of fixing.

Any other ideas?

Patrick