The 18GHz N-types- non-slotted outers- depend critically on uniform contact between the front of the outer on the plug and the step in the socket.
If contact is incomplete, suck-outs result as with your load. 18GHz plugs usually have flats to enable them to be torqued correctly- 1.5 N.m
For general use at frequencies up to 11 GHz I prefer the slotted outers, as they engage against the sides of the socket outer and torque is less critical.
7/16 DIN connectors require contact as the 18GHz N types and this requires very considerable torque- 25 N.m.
Alwyn Seeds, Director
114 Beaufort Street,
SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.