Get your engineers to refit the tail rotor assy and the old pitch change links. Fit Hydraulic rig and check that the tail rotor stops under the cabin floor are contacted at full left/right pedal. Then check the dimensions for the pitch change spider/tail rotor shaft dimensions at full left/right pedal as per maintenance manual. This will prove if there is a rigging fault. A very easy check to carry out with a rigging kit and hydraulic rig.
Do a wear check on the pitch change bearings to check within serviceable limits eliminates another possibility and change the pitch change links for new ones the damage is nasty! Do a spider bearing wear check to ascertain serviceable. The damage to the rest of the tail rotor looks ok in the pictures, but check the manuals/eurocopter for advise.
As for how the damage has occured maybe it is a little early to tell until further checks have been carried out, but it is very strange that it has occured on both of your machines. The main point is that the damage has been found and that you can rectify the problem safely. Work closely with your engineers as it dos'nt help when we blame one another, we are all professionals who want to these machines operated and maintained safely