Thanks for your reply. The function that forms the udf is in repos and the udf is registered and called in a notebook which is not. For most tests I am registering the udf in the notebook, after importing the function, however I have also tested registering the udf in the file that it's written (with the udf decorator), and also running the application of the udf in a file in the repo instead of the notebook and I'm still getting the same error everywhere.