As i was facing issues with the grader (all 3 tests 0 points) even i was convinced, my code is good, i would like to share how i solved it.
As per previous QA discussions and the notebook comments, it is often mentioned that global variables are not taken into consideration by the grader.
Therefore inside the notebook i was misslead by the hint (“you already coded it previously”).
To get the proper grading i therefore changed the model reference to create a new model from the class:
model = create_and_compile_model()
It did the trick for me. I hope this helps anybody.
BR