Import Update Matching from within same File

I'm having some trouble with importing from within the same file. In one instance it works and another instance it does not.

The scenario: two related tables - 1. Log table and 2. a Returns table. A script finds particular records in the Log table and imports them into an empty Returns table where the user can manipulate the data. Then, I'd like them to import those records back into the Log table with the updated information. (The Returns table then deletes all records; it is just a temporary storage place for the user to do some things).

Importing from the Log to the Returns table works fine. This adds new records.

Importing from the Returns table back to the Log table works when I manually set the Source table and line up the matching field and updating fields. However, I'd like to do this as "Perform without dialog".

Going from Log to Return, FMP remembers the source table, so I can "Perform without dialog". However, going from Return to Log, it does not remember the source table.

In both cases I am doing the following:

1. Getting a found set in the Source table.

2. Opening a new window.

3. Navigating the new window to a Target table layout.

There is always at least one record in the Source table.

Can anyone tell me what I am doing wrong?

Thanks.