This is unfortunately required in 2D Animation 7
To resolve this, please select all the Sprite swap frames in the Animation window and set (Both Tangents -> Constant) and (Broken).
Please refer to our documentation for more information:
https://docs.unity3d.com/Packages/com.unity.2d.animation@7.0/manual/FFanimation.html?q=constant#changing-the-keyframe-tangent