In the begging, the same, later from October 2018 it was just a steady decline. I'm pretty sure that this update has something to do with links and anchor test because I still have 2 stubborn posts that didn't fully recover. The ranking was stable and all of a sudden the keywords that I target with those 2 posts started to dance like crazy around 17th. On-page SEO is spot on, the same as other posts ranking 1 and 2. There are no 301s, I've never done them. So it must be links and/or anchor text. To tell you how sensitive google is to anchor text here is a short story. A few weeks ago I've created around 10 web 2.0 links targeting brand new post that was ranking on page 3 without any links with exact keyword anchor. Within a week they went down to the 10th page of SERP and below. Seeing what was going on I want back and changed the anchor text, I also edited the articles a bit to make google think that not only anchor text has changed. Sure enough within 10 days, they went right back where they were and now some are on 1st and the rest on the 2nd page of SERP.