Sad truth with many retailers is if it runs its fine!
Have a look at the Hornby Mag.,March, booster review main picture,the fault is obvious to see.
As previously reported I have mitigated the issue by adding shims.This fixes the wheels in contact with track problem but not the underlying fault.
In my opinion the problem is the screwed on side panel of the gear tower is not aligned properly causing the axles to sit out of true.
This may be a manufacturing issue or perhaps damage in transit.
This problem does seem relatively widespread. EFE should really respond.