I've noticed that the engine (Stockfish 9) evaluates positions as significantly better for white if the evaluation is performed while white is on the move. The difference is sometimes more than half a point.
Someone else has noticed this phenomenon, and anyone has an idea what the reason is (It's not run time, as I've let the engine evaluate above 26 PLY in both cases).
To clarify: The intention here is NOT the same position, just switching who's on the move. I will examplify by the start position. Imagine evaluating it and the engine gives +0.7 and gives the 1. e4 e5. Then you make the move 1.e4 and let the engine evaluate again, and now it gives only +0.2 and recommends 1.. e5.