Trade Officer
Hi Nick
That is an awkward gap. It is too small to sleeve it unless you have access to a lathe! I assume Hornby did it for ease of assembly
I don’t know if something like loctite 641 bearing retaining compound will fill that sort of gap. Probably not. Possibly 2 part epoxy? Making replacement if needed in the future, difficult
Either way you will need to make sure it is assembled square. How easy that is depends on the how much actual slop there is
John