W1 Assignment: How to check detailed information about grading?

I got 80/100 for this assignment (gradient checking), but I am not sure what it means in the screenshot below. I passed all tests and got all expected results. Just would like to figure out the part that I did it wrong.

Thank you!

Sorry, but that’s the most detailed feedback you can get from the grader in this case. The problem is that the test cases in the notebook can’t catch all possible errors. The distressing part is that the grader can’t even manage to tell you which function is the one that has the error. We have complained to the course staff about this, but apparently it is not easy to fix.

I will contact you by DM to see what we can do.