Good afternoon. In general, NXOpen methods should return an exception, rather than posting an interactive dialog, except of course in cases where you are using an NXOpen method specifically to post a dialog. That way the programmer can decide how a given condition is handled, rather than stopping the program to wait for input.
Please contact GTAC and provide a small program (and a part, if necessary) that will allow us to reproduce this, so that we can refer it to development for resolution. Thanks!