Keyframes don't replay when variant label changes

[ShahriarKh]

Using the same keyframes sequence for opacity in different variants only animates on the first render. Also, the opacity stays at the last value in the next renders.

https://codesandbox.io/s/angry-raman-bc9sf?file=/src/App.js

Steps to reproduce the behavior:

1. Go to codesandbox link above.
2. Click on "X" Button to toggle state (& fire animation)
3. See problem

Expected behavior
The box should go from opacity: 0 to opacity: 1 on every click.

Changing the other keyframe to another value with a little difference works correctly:
[0, 1] for both variants => animaties on initial render and stays on 1
[0, 1] for one and [0, 1.01] for another => works correctly

Question on Stackoverflow:
https://stackoverflow.com/questions/69887735/framer-motion-opacity-keyframe-only-animates-on-initial-render