I have read that "in a junction table, you need to set the primary key to
include the primary key fields from the other two tables. "

If I do this, I keep getting the error message "the change you requested to
the table were not successful because they would create duplicate values in
the index, primary key, or relationship.

The only way I'm entering data is through a form based on a query which
automatically writes to all 3 tables (the junction and 2 parents) at once.

If I remove the primary keys in the junction tables, I no longer get the
error message. Am I going to regret this later?

Thanks.