Just thought i'd post this for you guys, came into effect yesterday.

Google's Mobile Interstitial & Popup Change Now Live: What to Know

https://webmasters.googleblog.com/20...ontent-on.html

Copying exactly off Google Webmasters Blog:
January 10, 2017 update: Starting today, pages where content is not easily accessible to a user on the transition from the mobile search results may not rank as high. As we said, this new signal is just one of hundreds of signals that are used in ranking and the intent of the search query is still a very strong signal, so a page may still rank highly if it has great, relevant content. Please head to the webmaster forums if you have any questions.

There's been plenty of warning about this one, so hope none of you have been hit, and if you have then it's an easy fix