Hi nameLive,
In your project, the 4th key is set to have broken tangents (see the curve editor). I am assuming that you copy/pasted the first key, which breaks tangents on the keys around it so as to not mess up their interpolation with the other keys.
Broken tangents will cause those harsh transforms those harsh transforms. You can simply select your 4th key(s) and set Cubic (Auto) interpolation again.