Could there possibly be a carbon layer where contact is made? It wouldn’t destroy the plugs as much as direct piston contact but would still foul and possibly crack the ceramic of the plug.

 

I don't know the answer to that. I guess it is possible for carbon to accumulate in the combustion area if the plug was misfiring. Looking up the road also possible some damage might have been done to the involved injectors by the folks doing the repairs, don't know! Have you considered doing a compression test to rule out any cyl damage?