Playing West Somerset tonight and there is something I have noticed with this route. Most routes you can let off the throttle in a loco and it will coast when on level ground. Try a stock move near Minehead and try coasting, its like there is brake drag (they're all off). Has someone spilled glue or is this a physics skewed area. Seems a little too much rail friction
It is an old railroad, maybe the rails got to close to each other so the locos are lifting on their flanges? But it should be the opposite I think...
Have the brakes fully released? Some of the UK diesels have a nasty habit of not releasing all the way when you move the handle back to running. I find you need to pump into Release/Overcharge and even then can still have 0.1 or 0.2 shown on the loco brake cylinder. Also worth checking if you've applied the locomotive brake... As an aside that has caught me out on the US routes where I've used the "indie" as they call it to stop the locos, changed ends after shutting everything down then wondering why the brakes are dragging. Usually find it's because I forgot to release the loco brake and it doesn't come off from the other loco. Might even be a factor changing ends on UK locos.
Released as far as I could see at both ends yes. I’d had with some other services on route but always attributed to gradient
I believe that drag depends on the train rather than the route, for example I've tried the TGV (which maintains speed incredibly well while coasting) on SKA and it behaved like in LGV, while the ICE and the Talent especially felt like they had more drag. I also believe that TSW simulates the increased drag on curves, so if you are negotiating tight curves or points the train will feel more drag-y (is that even a word?) If I had to guess they tried to simulate the fact that the rails and rolling stock were not in an optimal state, which I guess it could make sense given it's a preserved railway.
I havent any problems on wsr. By the way, a worn out bogie moves usually better than one after overhaul with new grease and new brake shoes / discs etc. Not sure where your problems are coming from
Could it be the handbrake of the loco / stock? This would come close to a behavior like you mentioned