This is an example of what has happened to me any number of times while developing plug-in formulas.
I changed a couple of parameter names in a plug-in. When loading an old upr, I got this message:
The mistake is actually in a plug-in of a plug-in of a plug-in, but the error message refers only to the top-level formula, which is not in error. The missing parameters are not in the top-level formula.
Is it possible for the error message to be more precise?