Flying over smooth water was the worst condition for Green Satin/Blue Silk.
The design depended upon the signal being reflected back from the earths surface. Because this signal was transmitted forwards and backwards, it needed a 'rough' surface to send a reflection back. Over smooth water the signal simply 'skipped' away from the a/c.
The performance Akrotiri based a/c flying over the Med was far worse than my experience with Marham based a/c. Mind you, my 'main customer' was 13 Sqdn with Can PR9's that I believe flew slightly higher than 214's Valiant's.
In some instances the aircrew declined to tell me at what height the equipment did unlock!
Both the Green Satin and Blue Silk benches recieved many Tx/Rx's that were changed for 'Unlocking', that tested out fine on the bench.
The commonest 'real' problem with a Tx/Rx that was 'unlocking' was the Magnetron was shot.