Open_form still wants to direct the focus from one form (which is in enter-query mode) to another, and so the error 'Cannot navigate out of form' is raised.

That menu code after exit_form is never reached seems to be a feature of Forms, I came across this myself, and I have yet to find a solution for it.....

I am using headstart by the way which does not check for this status in this particular case (probably for the reason stated above), and also calls new_form even though in enter-query mode this is illegal. A bit buggy if you ask me....

An alternative might be to use exit_form in the when_window_decativated trigger, I have not tested this...