How to flip a bone without seeing "in between" two keyframes in play mode?

Hey! I am animating a character, that flips (through scaling a bone from 1 to -1 and then back to 1) twice during the animation, but in the play mode, in first flip, you can see "in between" key frames, even if there is absolutely no space between them. In the "curves" I have changed the both tangents to constant and linear, but none of it worked. The second flip looks fine. Does anyone have an idea, what could be a problem or even a solution? Thank you!