Since update 47 on console, I have had two separate instances where unknown master writs have dropped when they shouldn't. The first was a non-master crafter of only about level 18 received an unknown clothing writ. For the second instance, one of my fully leveled crafters just received 2 unknown woodworking writs from one reward box. It looks like something may have broken with the master writ drop rates, since neither of those should be happening.