So after 11,000 km the scooter suffered a failure.
My wife took the bike to work one morning and after about 1 km it suddenly felt very heavy and unresponsive to steer. She nursed it home and took the car. I had a look at it, suspecting a flat tyre but to my horror, the lower steering head bearing race was slopping around
So it appears that the headstock was machined to accommodate the bearing race, but with about 2 mm of metal to hold it in place! I tried tightening it but it simply refused to stay put. After every ride up the road it would kick out, increasing the trail to the point where it was completely unresponsive to input. So I put a jack under the bike, lifted the front wheel up and gave the race a whack with a hammer. It seemed to be centrally located so the next step was to weld it up. I'm sure I accidentally welded the bearing race to the headstock, but whatever, I don't want it coming off again.
Stick welding FTW.
Now it feels much better, but still less responsive than it used to be. I suspect it will just take some getting used to. If it still drives me nuts I can always pull the forks through the clamps and shorten the trail that way. Back on the road at least. Batteries are doing just fine.