Tracy,

Index On ALLTRIM(Transform(numfld)) tag numflda

How wide is the index key? Is it 1, 2, 3, 4, or more characters? Indexes in VFP are fixed length keys so everry entry will be the same length. To get your index to work you must pad it to a constant legnth that is as big or bigger than the largest value that will appear. To get a numeric sequence you must pad them on the left as in;

Index On PADL(ALLTRIM(Transform(numfld)),10) tag numflda

Now that indedx key will not be affected by any of the things you showed.

In answer to your question, in my opinion this is NOT a bug as the index key you were using has undefined results and therefore is not dependable.