It sounds more like a syntax error. Either that or perhaps you changed the function definition of get_score? The point is that in the notebook as given to you current_classifications is the first positional argument to get_score, but is not a “named” optional argument.
Just generally speaking, it’s not a good idea to make changes to the areas of the notebook outside the “YOUR CODE HERE” blocks. It’s not illegal, but you need to know what you’re doing when you step outside those bounds and to keep in mind that the grader is a “black box” and we’re not sure exactly what it may or may not be depending on. E.g. this thread is the canonical example of a surprising expectation on the part of the grader. It sounds like you’ve gone a bit too far in that direction. I agree that the next thing to try would be to start with a clean copy and just “copy/paste” over the “YOUR CODE HERE” sections and see what effect that has. You can find a topic about that on the DLS FAQ Thread. Let me know if you have trouble seeing that thread.