This is arguably more of a bug report but I've noticed lately that in analysis the engine sometimes flags as inaccuracy a so called "not the best checkmate sequence", even when the number of moves is not actually higher.
Here is an example in my latest game: http://en.lichess.org/FL3PXf9I/black
Here is an example in my latest game: http://en.lichess.org/FL3PXf9I/black