Hi Haakon,
Thanks for your thoughts. A few rums last night stimulated the logic that it may have nothing to do with the Hall sensors at all. If the Hall sensor were wrongly installed, it should manifest the problem when cold, but it doe snot. It may be in the wires connected to the Hall sensors or, indeed, somewhere else in the wiring loom. We will start at the Hall sensor plate, do the adjustment with a dial gauge in accordance with the GS911 procedure and see if that does the trick. If not, we will have to go through the wiring loom to see if we can find a bare wire somewhere.
The plastic sheath on the wiring loom is badly disintegrating. That seems to be a common fault with BMW wiring on newer bikes. My 2005 BMW R1200GS loom is cloth taped - all a bit last century. It seems that what works in Europe often does not work in Australia. I do not see wiring looms on old Japanese bikes deteriorating to the extent that European bikes do; i.e. not just BMWs. For example, the rubber boots at the paralever pivot and gearbox spline output on my GS lasted only 5 years before perishing and splitting. The rubber boot on the telelever ball joint split after about 6 years. That costs you a whole ball joint - not that expensive in the scheme of things, but irritating nonetheless.
While I am banging on about reduced BMW quality, BMW has a big problem on its hands with the spoked rims on the new LC GS. They are rubbish. A mate has damaged 2 rims in 10,000km on his, basically doing graded dirt roads. The rims are weaker than the rubbish rims on 950 KTMs. BMW is currently refusing to replace the rims on warranty - OEM front wheel replacement cost - AUD2,200. The spoke nipples are too close to the outside of the rim and the metal is cheese. I will wager the LC adventure comes out with different rims.
I will let you know how we get on with the S.