A couple of our Sunset locomotives lift one of the front wheels off the rail unless the track is totally flat and smooth. In certain spots this causes a derailment. I've disassembled the pilot truck, tried reversing it, loosening the screws/springs holding it, but it still lifts the wheel, usually the inner one on the curving section of track. It used to go air-borne at the slight change in track elevation coming off a long ROSS turnout, but loosening up the mounting screw allowed enough flop to keep it on the rail.
Hope it's not a "some engines do this, no fix" situation, or I have to ban all of them from the upper subdivision, which has minimum 80 curves.
Thought about bending the piece between the mounting on the frame and the truck frame, but Kyrian advised "NO!! Don't do that!!! .., see if there is a fix without bending up stuff"
Any advice is appreciated!