=>. (and it is =>only one point, which looks very flat and clean etc.) =>
=>Thanks, =>Neal.
That finding suggests that this particular turnout's measurement's are off, either at the points or at the frog (crossing) -- where exactly does the pony truck derail? Combined with excessive sideplay in the loco's trucks and/or a wheel set that's slightly off optimum meaurements (eg, gauge, back-to-back) and/or insufficient downward pressure on the truck, that's just asking for trouble.
You need a good gauge for checking wheel sets and turnout dimensions. Since UK manufacturers don't adhere to any standards (not even their own), that's going to be tough to find. I suggest either an an NMRA gauge, and making all your trackwork and wheels conform to NMRA standards, in the absence of any UK standards (and the perennial refusal of the various True Scale groups to get together and work out a usable common standard for OO-16.5mm gauge.) I can supply NMRA gauges at my cost + postage, if you are interested. Shops that deal in North American outline should also have them.
HTH&GL
Wolf Kirchmeir ................................. If you didn't want to go to Chicago, why did you get on this train? (Garrison Keillor)