Legal advice - 403(b) plan

My father who passed away last year had a small 403(b) plan with Lincoln Financial Group and only listed my mother as the beneficiary. We have an order from the court of possession of said assets, but LFG is going by the plan documents which states the balance is to go to his estate.

We did not create an estate for my father's assets. My sister was listed as executor in his will.

My question is should the court order trump the plan documents? Or do the plan documents prevail?

We are having a hard time opening an estate account for my father since he has passed away.

TIA.