Hi all. Here is a update on the problem, we have had with the BS-170. I discovered that the ground of the wired remote input of the radio was on a separate circuit and not part of the normal grounding circuit. That meant that the BS-170 was floating, causing it to malfunction. I replaced the BS-170 with a TLP221AF photorelay, and at this stage the circuit is working 100%. Thanks all for the input.