Why does vertical animation have horizontal deflection?

Question

css

If you open this codepen example in firefox and click on the scene, you will notice that the animation is quite acceptable. But if you enlarge the window in which the code is executed, you will notice that when the rectangle finishes the animation from the bottom up, then at the very last moment there is a terrible horizontal shift.

And this horror happens only in FireFox. What is the reason and how to fix it?