2 x PowerNode with no speaker output

Have 2 x PowerNode N150 (gen 1) and both units have stopped outputting sound. Both units have working logic and they have the latest firmware installed. I can control both units from a controller and they respond properly as they should.

The relay click is missing from both apart from one unit booted up with relay click 2 times, when that happened I started playing music and connected the speaker wires afterwards (wasn't hooked when I booted) and that worked with sound output so it's something with the relay not being activated and letting sound output go to the speaker terminals. I've opened both units to inspect and cannot see any suspicious (like leakage from capacitors etc.).

Clearly if I have 2 out 2 units (not bought at the same time) which have failed the same way this must have happened to other users and not just me? I've submitted a support request hoping that BlueSound can direct me to the specific component(s) as I assume this will be too costly to send for repairs. It would be a shame to recycle as it's working apart from the issue described. There was another old thread about someone replacing components on the DDFA board (and as I understand it) and got information from BlueSound on what to replace but that was due to the amplifier was in "protect" mode. 

If anybody has either the same experience or a possible solution please reply to this thread - thanks!