First let me apologise for the lack of specificity atm. I'm writing this at the end of my work day after I worked around the issue, so I'm writing this from memory. I do hope to come back and fill in some details, provide proper code, etc, but I may be told to focus my time/energy elsewhere now that our code is working again(🙄) 🙏

Using version 0.50.1, I encountered a NameError in the sources.get_source call, and traceback took me through utils.unmarshal_json to the unmarshal.from_dict call (and then into dataclasses_json library).
It seems to be choking on the models.SourceE2eTestCloud use in models.SourceConfiguration, as the NameError mentions that ContinuousFeed cannot be found (?, apologies, I've forgotten the exact message).