Structure-specific mobs aren't spawning in previously discovered chunks. After 1.18 released, I transferred my PS4 long-term survival world to bedrock, and that's when I noticed some weird things begin to happen. I have two ocean monuments I use regularly, but neither of them are spawning guardians anymore. On top of that, I'm having weird spawns in the nether. Wither skeletons and blazes are spawning in weird places outside of the fortress, mainly my pathway I built before updating connecting my portals. biome-specific mobs seem to spawn just fine. I have not tested to see if these mobs spawn in newly generated chunks yet. Let me know if you need more info. I haven't played Minecraft in MONTHS thanks to this glitch!