Sorry for not getting a clear example. Here is a clear one (
lichess.org/3FuxKxSV#82).
42.hxg6 the score drops from 13 to 9.7 even though this is the best move by Stockfish 10 on my computer. The same with 42...Kg7 (the score drops to 61 though this is the best move).
The 61 score is the score of the 2nd best-move 42...,fxg6??.
31...Ra5 is again the best move by Stockfish 10 (starting from low depths) but the js version gives a drop of 0.5 (which might again be the score of the 2nd best move)
One can find more examples of this phenomenon in other moves of this game.
Ofer