RF Circulators

I am designing a system that uses a Circulator in order to multiplex Tx and Rx onto one antenna/cable assembly. I am having problems with the system and all things point to the circulator as being the culprit.

Does anyone have practical experience with PCB mounted circulators & what to watch out for? Basically the system works well provided the cable between the PCB and the antenna is a certain multiple of transmission wavelength. I can insert a phase shifter in between the cable and the PCB and if I adjust the phase I can make the system selectively work or fail. I can also place a conductive object near the circulator and get it to selectively work or fail.

I am using a small magnetic circulator that is designed for surface mounting on a PCB. It is soldered down by it's terminals but the body is not soldered down, so it's body is not strongly connected to the PCB.

Is it required to have the body soldered down or bolted down to the PCB? Can the electrical properties of the circulator be modulated by the proximity of ferrous materials and if so how can I avoid this?

Thanks!!!!