Editing a downloaded roster deletes created players?

I'm not sure if this is a bug, missing feature, or for some reason something intended, but I wanted to ask if there was a way to fix it.

When I download a roster (currently the latest Tactix one) and edit a player in it, it deletes all of the created players and teams once I save it. It's annoying because I want to tweak some player ratings without losing out on the huge number of created prospects. Is there a way around this?

Thanks.