Delayed claim, delayed funeral!

My brother passed away, he nominated my mother as the beneficiary on his policy. My mother submitted the required documents in the branch and everything was well. She later on received an sms saying she must submit a Letter of Authority. Why should she send letter of authority whereas she is the nominated beneficiary. How do you expect her to bury his son if you keep delaying this payout. Your documents says letter of authority is only required if theres's no beneficiary nominated. Why change the rules in this case?