Likewise I have been using Bachman metal wheels for over 2 decades now with few problems. I have encountered the odd out of gauge or wobbly one. These have been swopped out, key is to record wagon and location over a few running sessions. If tis the same wagon test out with eye to track to see what is occuring and which wheel, thus identified take that one out of wagon to examine it carefully. Roll along the track does it wobbke? Try it through a point does it go smoothly past the safety rail. All dead simple logical stuff to do.