I have a world where I have been building more onto an existing village. I had 3 composters, each with a master-level farmer villager assigned to them, each with 2 blocks of open space in between them. I had this for a while, and one day I saw there were two more novice-level farmer villagers. I was confused, as I hadn't placed any more composters. I investigated, and saw that they were using the composters that had previously been used by two of my master-level villagers. I had never broken any of the blocks; they kind of just started working there. Because my other farmer villagers were master-leveled, they wouldn't become jobless, so I was stuck with two master-leveled farmer villagers that wouldn't be able to restock their trades. I tried breaking the composters and assigning the novice-level villagers to new jobs, but now the master-level ones won't claim their respective job blocks. This also has happened with master-level villager working at a smithing table in a similar manner. I'm not sure what I should do. The novice-level villagers mentioned here spawned naturally as I expanded the village and placed more beds, so I'm not sure if that has anything to do with it. I had seen that someone had posted a similar issue, but they were in an older version and it had been invalidated as they were using datapacks. I had no mods or datapacks on at the time, so it couldn't have been caused by that. I was also in creative mode, so I'm not sure if that changes anything.

     I'm not sure exactly how to reproduce this glitch, but if you have a job block, completely level up the villager that works there and allow a villager to spawn naturally, it may "steal" the job block. It's not game-breaking, but it's definitely annoying to say the least.