Hi @trainboy, I have not seen this problem but I suggest you turn the loco upside down and place it on something soft to protect the roof detail. Then try turning each wheel set in turn. If anyone or more of them are free to rotate then they have a problem, maybe you have done this already. If you have an issue you could email IRM support as they have a lifetime warranty or alternatively remove the axle keeper plate and see if the gear on the axle is loose or damaged. If it’s damaged you will need a replacement, if it’s loose I’d still look for a replacement. Hope that helps.