For debugging purposes I add a string field called FORM_VERSION to my surveys that pulls the form version number found on the settings tab. I increase one of the version numbers each time I make a substantive change to the form and want to differentiate results between versions (e.g., when adding a new field, I can quickly identify why certain rows have nulls).
Pulling the form version is easy in Survey123. Just add version() to the calculation column of the XLS form.
The Survey123 mobile/desktop apps support this. The Survey123 web form does not support the version() calculation. Can support for this calculation be added to the web app?
Here's a public survey for testing/validation. If you add any invalid test data, please let me know.