Middle axle differential problem of a SANY SY410 Mixer Truck (10m3)

Hi everyone , We recenty had a middle axle differential problem of a SANY SY410 Mixer Truck (10m3) , as u can see on that picture these are the parts that we lost ; Adding to that I should informe u on the specific detail : · The Customer was quite late on the maintenance , say like 2 month late · The Customer had also canceled the braking system on the left side of the middle axle differential I suspect that this also could one of the roots of the problem · Very poor cleaning on the customer is done its quite dirty Thus I want to know what could be the root problem that could cause this problem ? Is it manupulating and operation ? Quality materials ? Poor cleaning and maintenance , braking system on the axle side canceled …. ?