OFX import function working just one time

[Henry De la Mano Malaver]

Why the import function by OFX file can't work more than one time?

When I import an OFX file, It's working just the first time, because
even when I pick up another file, the import function brought  empty 
transactions.

If I delete the  imported previously transactions, I can Import 
succesfully again.

We have to do a lot of imports over time to avoid them manually.