Modifying subform's underlying SQL statement

aI am trying to make modifications to the the SQL statement underlying a
subform. I make changes using the query builder. However, after I make the
changes and save the updates my changes just disappear. This happens
regardless of what changes I make, e.g. I tried to add new columns, I tried
to add new "where" criteria. After making the changes I close the builder and
confirm that I do want to save the changes to the SQL statement.
Nevertheless my changes disappear.

Please help. I have been at it for hours.

DoDev