If too hard and no bump stops the shock absorber is transmitting the forces from the road springs directly onto that mounting, and this might have contributed to the failure.
I think this is a good point, Andy. With AVO shock absorbers there are 3 sizes giving different lengths of maximum extent and minimum compression and when we measured my car up we found that none of the standard options gave the right range of movement.
Fortunately Tim Ayres (New Elms) was able to get AVO to do me a set with a different range and everything is fine, but I wonder if a set of shock absorbers with an incorrect minimum length (ie won't go short enough) would act to transmit unwanted forces to that mounting?