Here is the correct answer if you remove the intentional errors in the back prop code:
Your backward propagation works perfectly fine! difference = 1.1890913024229996e-07
Interesting. That’s different from your answer in the 3rd decimal place, which is not a rounding error. So something must be wrong in your code, but it’s a subtle mistake.
It will help to see your code, but we can’t do that in a public thread. Please check your DMs for a message from me about how to share the code privately.