Unable to delete alternate on INIT page

[1mileup]

Hi, 

When i import a simbrief flight plan with a prefilled alternate on the INIT page, if I change my mind and wish to remove the alternate by typing NONE into that field the message 'airport not in database' appears and the field reverts back to whatever airport i originally had in there. If i simply try and clear the field then click enter it comes up with 'entry out of range'.  I can change it to another airport no problem but i can't remove it.  Trying to delete the airport from the end of the flight plan also doesn't work as the '*delete' field is greyed out and cannot be clicked on with the mouse.

Am i missing something really basic?  On every other Airbus type, typing NONE will remove the alternate from the end of the flight plan.

Appreciate any and all suggestions.