Scale reverts to 1 as soon as it is changed

I have a sprite animation where i flip the x axis at one point because the sprite i use at that point is flipped reversed to the other sprites. Of course i could edit the sprite but i wanted to try to do it this way. It worked. But as a consequence i found out, after 8h of debugging, that as long as this animation is used in the animator, no scaling can be done during runtime. Not from code and not from the editor/inspector. Well i think that what happens is that it scales back to 1 as soon as the scale is changed.

The animation sets the x rotation to 1 and then immediately after to -1 to show the flipped sprite correctly and then immediately again to 1.

The animation/state that is causing the trouble is reached with a trigger so it is only played when the kick button is pushed. Is this a known problem? Am i doing something wrong?