I think you've discovered another problem with the behaviour of the program when a new movie is being added this way. When you first click on "+", a blank entry is added to the top of the list. If you enter a title and apply changes, this should change to the title. Sometimes, howver, it does not. I'm not sure why, but maybe because filters are set so the new entry is hidden. Unfortunately, the blank entry remains at the top of the list and the new title remains in the pane on the right, creating the impression it is properly selected. In fact, the null record is still the active one, and the plugin search finds nothing.
It seems this troublesome behaviour can be avoided by
Resetting filters before selecting
New.
Hopefully nostra will fix this in the next update. However that is done, plugins should also detect the error of attempting to update a null record.
Thanks for your test results.