I assume it is an issue with the dataset, since we started having issues shortly after a data update from workbench.
Does anyone know how to troubleshoot such a generalized error message?
Look for missing fields, divisons by zero, Field names changes. Normaly the card editor gives you some ints or you can remove fields from the card one by one and isolate where the problem is.
Hope this helps.
I think there were some missing fields (even though I couldn't see them). The export showed the column names correctly, but a couple of the columns were showing blank values on records I recall previously having values.
We ended up building a new dataset with workbench and connected that to the related data flows.
Things are now working as expected.