.... Not for the usual reason.

I have a UDF that lives in a standard module in an add-in. The add-in
loads automatically. I have one workbook with two worksheets that call
the UDF. For some time I had no problems, but recently I tweaked one
of the worksheets. Now, that worksheet no longer recognizes the UDF
(returns #NAME). The other, untweaked worksheet works fine.

I made a copy of the UDF in the module where it resides, gave it a
different name, and adjusted the worksheet to call the new copy. Works
great. But surely I don't need to keep two identical copies of a UDF
in the same module... What could be going on here?

For what it's worth the add-in has dozens of UDFs (in other modules)
that work just fine. This is Ex2003 by the way.