It's good to have a plan! ?
Given what I have seen throughout this extended fault finding expedition of yours, I still think that somewhere you have a high resistance point, probably due to corrosion.
As with any intermittent problem, the challenge is finding the root cause, which can be very difficult.
This certainly is challenging, the auto electrician called in has he was close in the neighbour hood and had a quick look at all the earth that were easy to access and these were all removed and cleaned up, also tidied up some messed with before wiring that had been for the now removed PTO. Unfortunately it was only a quick call by buy told me to disconnect the fuel filter plug to see if that will make any difference.
A quick drive up the road a few days later and it still had the safe mode come in. It is really only when the lorry wants too go into safe mode that it will.
I drove up north last week and have noticed it going into safe mode a bit more than normal, so with on the move I depress the clutch pedal and once the revs drop to under 1200 rpm's the orange light go out and then I can carry on my way. However the lorry came back on the back of a breakdown service as I stopped to ask directions and when I got back in to start it up it didn't want to know, first thoughts were a dicky starter motor. The Honda garage I asked directions at put their jump pack on it and it mad no difference, still sounded like the battery was flat. The AA were then within 40 minutes and were stomped are over an hour trying to get it running, even tried crash starting but as soon as the clutch was let off the ignition lights went out and she was a no go! She back home now after 3 different recovery vehicle services were called, broke down 10:30 am Wednesday and finally back home Friday morning at 11am.....Yep not impressed!
I removed the starting motor and it worked fine, reinstalled it and it would not work, so took it to have it checked and worked fine on the bench, however put a small load on it and it wouldn't work even after various tests. Amazing that it failed without any warning whatso ever. New starter on the way and should be here Friday. Then I can get the auto electrician back when he comes back from holidays.
Blink code was still throwing up Camshaft Timing Sensor. Possibly a weak spot in the wiring, which would account for the low voltage fault during the ECU check? Would this also mean what you have said about a high resistance Skifreak?