I have this locomotive for several years and had it upgraded by Bachmann a couple of years ago to the version 5 frame.

Recently I have had a problem with the engine staying on the rails. I thought it might be heating and cooling of the rails affecting spacing.

I now find the front drive wheels (with the flange) are 'wobbling' on the shaft. The left side (looking from the Engineers view) being worse than the right side. The 'wobble' is so bad I think it may allow the wheel to drop between the rails.

It this 'wobble' normal and have I just not noticed it before or do I need to send it back for another rebuild?