Locked pawn structure, analysis (engine test)

http://en.lichess.org/MKxoutpt/black#107

I don't really understand why the evaluation suddenly drops (engine recognises draw), but then rises immediately, despite identical analysis time (I don't think it's the horizon effect, long local-analysis still says +10)

Analysis is parallelized across multiple servers and multiple Stockfishes so it runs faster, but at a risk: there is the possibility that not all the servers generate similar evaluations for similar positions.

Stockfish is not designed to analyse this kind of positions.
For thematic draws, it's more suitable to use Sting-SF : http://www.talkchess.com/forum/viewtopic.php?t=58839