The biggest factor I've seen is them pruning and devaluing links, but not in every instance, so it's still a bit of a head scratcher. That's nothing new when it comes to these updates. I personally think Google is constantly tweaking ranking signals. Think of it like a +/- system. This update may give more weight to title tags, or H tags and diminish the value of other factors. Then they tweak the next update to give a "+" to other ranking signals, while dialing back on previous signals that they gave weight to. It's all part of the game. Continue to stick to the fundamentals and over time you will see a net gain on traffic and rankings. Understand that there are going to be times in the life of your website, which you lose rankings and traffic. It's part of the game and something you need to accept as an SEO if you are going to succeed.
