Update...
The loose pad was a red herring. The actual problem was the pots and the ADC (analogue to digital converter chip) for main volume and rotary speaker drive. I noticed that the NS2 only booted up when they were on their maximum value. I changed them all and the machine boots up regardless of volume level.
I also had a lot of LED ghosting (some LEDs glowing when they should be off), which I traced to some bad LEDs (all green!), I'm in the process of changing these.
The last issue, where some parameters were randomly changing, appears to be on the control board 2 - I need to change 4 pots.
Maybe this helps someone else. But please don't attempt repairs unless you know what you are doing.