Varioguide serial interface cable.

Apologies in advance as technically this is a hardware issue rather than a Precision Farming question.
Is anyone using the Varioguide D-sub 9 pin connector in the roof of their Fendt tractor?
We are finding the locking nuts project quite a bit lower than a standard plug and the new cable we have barely makes any contact when attached.
Are all D-sub plugs a standard size?