Os Maesters da Patrulha da Noite têm Juramentos conflitantes?

Não parece, na verdade, eles são bastante semelhantes.

Juramento do Relógio da Noite

Night gathers, and now my watch begins. It shall not end until my death. I shall take no wife, hold no lands³, father no children⁴. I shall wear no crowns and win no glory¹. I shall live and die at my post. I am the sword in the darkness. I am the watcher on the walls. I am the fire that burns against the cold, the light that brings the dawn, the horn that wakes the sleepers, the shield that guards the realms of men². I pledge my life and honor to the Night's Watch, for this night and all the nights to come.

Votos dos Maestros

Não há menção específica ao que os votos dos meistress são, mas o que segue é o que eu encontrei sobre eles.

1. Coloque de lado o nome da casa

A toothless smile quivered on the ancient lips. "Only a maester of the Citadel, bound in service to Castle Black and the Night's Watch. In my order, we put aside our house names when we take our vows and don the collar." The old man touched the maester's chain that hung loosely around his thin, fleshless neck.
_{A Game of Thrones, Jon VIII}

2. Sirva o reino

"He told me that a maester's collar is made of chain to remind him that he is sworn to serve," Jon said, remembering. "I asked why each link was a different metal. A silver chain would look much finer with his grey robes, I said. Maester Luwin laughed. A maester forges his chain with study, he told me. The different metals are each a different kind of learning, gold for the study of money and accounts, silver for healing, iron for warcraft. And he said there were other meanings as well. The collar is supposed to remind a maester of the realm he serves, isn't that so? Lords are gold and knights steel, but two links can't make a chain. You also need silver and iron and lead, tin and copper and bronze and all the rest, and those are farmers and smiths and merchants and the like. A chain needs all sorts of metals, and a land needs all sorts of people."
_{A Game of Thrones, Jon V}

3. Não segure terras ou senhorios

Grand Maester Pycelle did not disappoint her. "Lord Qyburn?" he managed, purpling. "Your Grace, this . . . a maester swears sacred vows, to hold no lands or lordships . . ."
_{A Feast for Crows, Cersei IV}

4. Pai sem filhos

When a maester donned his collar, he put aside the hope of children, yet Cressen had oft felt a father nonetheless. Robert, Stannis, Renly . . . three sons he had raised after the angry sea claimed Lord Steffon. Had he done so ill that now he must watch one kill the other? He could not allow it, would not allow it.
_{A Clash of Kings, Prologue}

Assim como os Novatos e Noviços do Night's Watch podem deixar o pedido antes de se tornarem um Meistre.

That was many years ago, to be sure. The boy of sixteen was a man past forty now, and his legend had grown a deal darker. He had traveled in the Free Cities, learning the poisoner's trade and perhaps arts darker still, if rumors could be believed. He had studied at the Citadel, going so far as to forge six links of a maester's chain before he grew bored. He had soldiered in the Disputed Lands across the narrow sea, riding with the Second Sons for a time before forming his own company. His tourneys, his battles, his duels, his horses, his carnality . . . it was said that he bedded men and women both, and had begotten bastard girls all over Dorne. The sand snakes, men called his daughters. So far as Tyrion had heard, Prince Oberyn had never fathered a son.
_{A Storm of Swords, Tyrion V}

Note que a Citadel é conhecida por chutar um maester fora da ordem, mas isso ainda não entraria em conflito com o juramento da Night's Watch.

"The Citadel took my chain." Qyburn put away his needle. "I should do something about that wound above your eye as well. The flesh is badly inflamed."
_{A Storm of Swords, Jaime IV}

Parece não haver contradições entre os votos, tanto quanto eu posso encontrar. De fato, ambos parecem se alinhar de várias maneiras (deixando de lado o nome da casa, o celibato, renunciando a reivindicações de títulos ou riqueza). Além disso, espera-se que os maestros façam votos e permaneçam leais aos castelos e senhores a quem servem, o que serve aos castelos e senhores da Patrulha Noturna.