As a matter of interest, are you saying the beneficiaries are being changed before, or after, the death of the testator, and who is changing them?
25 odd years ago when my father died a cousin was one nominated executor and the solicitor who wrote the will another. Neither wanted to do it, the solicitor presumably because there wasn't enough in it for him to bother and, my cousin knew nothing about it whatsoever until I told him. They both agreed that I could do it and I did. Exactly the same thing happened two years later when my mother died.