Oil pump lost its prime twice this year

[JP147]

A few months ago I put new seals in my EA81 oil pump because it was leaking heaps. That seemed to fix it but earlier this year the pump lost its prime. I pulled it off and it was empty. The only problem I could see was that there was a burr at one of the small o rings where someone had tried to remove it with a hard tool. I sanded it down and reassembled the pump with fatter o rings and sealant and it was good for over a month but now it has lost its prime again.
Any ideas what is wrong with it? I think I will get a new pump if I can find one.