First time for this:
Changes to a combo setting push a message to user offering to replace the contents of a "Master" DBF field.

When the code instructs:
replace MyDBF.MyField with lcSomeValue - it does not take.

However, when code instructs:
select MyDBF
replace MyField with lcSomeValue - it takes.

It's one little interactive procedure. A form deactivate fires a "custom" data session object in service of a MESSAGEBOX just before the REPLACE. Maybe some foobar character codes hidden in the PRG file. Just weeeeerd.

The "->" field pointer has same non-result.