I've seen this also, all of the competitors that are on page one don't have the keyword in their backlinks and the one big brand name competitor which has been on page one a long time is even slipping because they have a lot of this specific keyword anchor as their main anchor text
I tried to keep my brand name as the main anchor text and I've gradually slipped from 3rd to 14th since Penguin 2.0 but its happened very slowly... and Tuesdays tweak made it drop a couple of spots but its hanging on so I must have done something right.
I didn't use anything obviously blackhat but I've bought a couple of High Pr/Good Trust Flow links recently including Sape, obviosuly with pressure from my client its not helping... I'm hoping this is just a dance and things will settle... my anchor text is about 30% keyword and 30% brand in Ahrefs but one of the competitors is higher with 1000's of anchors for this keyword as their main keyword(but like I said they have been slipping to 10-11th just ahead of us)
What do you think guys, do adding Sape links cause dancing like this? I bought about 20 sape links from one provider and some other Sape links from some Russian sites.. so not major vendors that would be on Google's radar. It started slipping before I bought the Sape links, don't think they've even been processed by Googlebot yet so I'm thinking its anchor text variation for sure