GDK16 line issue

[Bluemooner]

I have a customer who has 2 lines on a gdk16 basic ksu.
they have an intermitant fault where on both line 1 and 2 when they press 9 for an outside line they get external dial tone but when they press the keys to dial nothing happens. it only happens on external calls and its not just on one handset its on all of them

 

[doktor]

Do you use ISDN (BRA) or Analog lines?
Is the system properly grounded?
What s/w level is used? [Tans/Pgm]+40?

///doktor