If it's really every other night for two in-game weeks, that's pushing "possible" to an incredulously unlikely point. 50% of nights isn't impossible for a few straight nights, but 14? If the OP isn't exaggerating and they're not *staggeringly* unlucky, then there is a bug causing the rate to be higher than expected. My own playthrough hasn't experienced the same thing so it's got to be something specific triggering it in OP's world and not mine.
All that said it's possible that the rate is intended to be higher in Master Mode, and even small increases in rate quickly add up. If it's double, say 22% per night, then OP's unlucky streak still sucks, but falls a lot closer to the expected bell curve.
OP, try to keep explicit notes on the Blood Moon rate you're experiencing. Include Moon Phase if possible since that is the closest thing to a day of the week that the game has, and because New Moon is the one day of the "week" that Blood Moons are impossible.