02 Disco rear diff, Help!

Can someone please tell me why on my Disco 2 that my rear diff bolt has been breaking in half over and over. I am so upset that I can not figure out why this is happening. This is the 3rd time I had to tap and drill the bolt out. I have asked many mechanics and no answere everyone is puzzeled. HELP ME PLEASE
Michael

which bolt

The rear pinion bolt

rear diff bolt

overtightening ? how far down does end of pinion sit 2mm from washer on flange ?bolt too long

Stock lanrover bolt, where are the forces coming from to break these bolts

i presume its 3 bolt flange with rubber doughnut,when flange is pushed over pinion pinion dosent come to end of flange so that bolt pushes flange onto brgs,to give with right shims correct preload,i would find out if flange ,pinion,etc are good and settings right

thank you for your time in this matter i will check and get back to you. thanks again,
michael