Interesting Columbo. Are you saying in fact that the bogies didn't have sufficent longtitudinal movement to allow them to 'tip' or 'rock' as they negotiated your pointwork and as a result one or more of the wheel flanges was rising above the rail head. If that is what was happening doesn't that put a question mark over the longtitudinal level of your track? I suppose but fact that the rest of your stock is OK the level can't be that far adrift though. I must admit, I did have a similar problem with a rake of Bachmann BYA's but that on investigation that turned out to be the screw that retains the buckeye coupling plate was fouling the the bogie and preventing it from 'rocking' on its king post.