count_vectorizer.vocabulary_.items() and count_vectorizer.vocabulary_ Inconsistent number of returns
For future readers: as Ben wrote in the comments, it is really hard in general that len(my_dict) != len(my_dict.items()). When these kind of strage behaviours happen, it is always a good practise to perform some routine checks:


Clean your environment from every variable, even better restart the kernel and then run again your code.
Check your code for variables with same name, be sure you're not overwriting stuff, it's easy also to end up defining functions with same name of other imported library functions.
Try your code on different datasets, to be sure the mistake is not due to some external issue with the data. 


If none of the above checks solve the mystery, then you can start thinking about a bug, a corrupted installation of a library or some other more nested problems.