XRAY - Model racing cars

Sorry if I seem to be moaning a lot about this car but its just that i want it spot on !
Has anyone else noticed that the centre diff moves back and forth in the mount ? Is there a reason for this or is it a tolerance problem ? The reason i ask is that this could be whats causing the spur to break because, if the diff moves back then it can make the teeth run on the inner part of the bell which is slightly proud of the bell tooth root and cause a failure. This would explain why a looser gear mesh is solving the problem when really the solution might be to shim the diff and stop the movement. What do you think ?

I already have brought up this question in januari, when I build a couple of xb8 all the cars had that play in the centre diff mounts, I shimed it from the start and mounted a t spur since day one, No failure at all, not a broken part in almost 3 gallons, so im impressed of the car, the handling are superb its just a tad loose in the rear but I hope i can fix this with a bit more testing

if i take off the top mount there is play of about 2mm back and forth but no signs of movement when the diff is complete (strange) , maybe the two bottom mounts splay outwards and when the top is fitted the splay out is corrected ?? maybe ?