I upgraded DSS from 5.0.4 to 5.1.1, and now I'm getting the error shown below for any Python formula in a Prepare recipe that returns a row or rows. Even the default code returns the error. Standalone Python recipes, as well as formulas in Prepare recipes that only return a cell, work just fine. I have updated the Python code environment as indicated by the upgrade instructions, and I have tried changing the project's code environment (including using the DSS's builtin environment option).
Any ideas? If I don't resolve this soon I'll have to try rolling back to 5.0.4.