Is the record source of the form a saved query itself? If so ... then if you are in form design, open the record source (query) by clicking on the 3 dots - then modify that (saved) query >> ie
"What I usually do is double click the field that I want to add. Most recently, I attempted to (1) remove one query from the record source, and (2) replace a table in the record source with a query based on two tables."
>> then at *that* point, you have to save the query, *before* you go back to form design view. Otherwise, the changes you made to the saved query will not be ... saved. This would not be the case IF ... your form's record source was a SQL statement that you created for that form.
mx