Short description of error
I was not able to figure out the exact steps to reproduce this, but I have a file that loads the error every time I play it.
So I have an empty that is having an animation for its rotation, (empty located to 0,0,0) and then I have a camera which is parented to the empty and the camera has an animation to make it move to the z-axis. I added for both of those animations the cycles modifier and after that the stepped modifier. Now it seems that the rotation is happening 1 frame later than the movement even tho I have exactly same F-curve for both animations. So the rotation animation is not following the F-curve in my file. Image of my setup: https://i.imgur.com/b9Tnnr1.png
I "fixed" the problem by adding 1 frame offset for the stepped modifier. Later when I played with the keyframes, the problem disappeared and I could not reproduce it, so this blend file is only proof that such error even happens sometimes. Blend file: https://www.dropbox.com/s/jhs4za2tlfrpg9l/tetris%20-%20Copy.blend?dl=0