I did not find any overwriting of the data.
Using the JMP Sample data table, called Probe.jmp I ran a Fit Y by X, specifying DieX as the Y, Response and 37 numeric columns as the X, Factors
Holding the CNTL key down, I clicked on the red triangle and selected Save Probability Formula
The data table started out with 394 columns, and ended up with 616.
Each of the 37 parameters created 6 columns,. Each set of columns are unique and based upon a different Y response for each of them.
What did I do that was differant from what you did?
Jim