Hi. I've been experiencing the bug for the latest versions. Mobs seem to stop spawning completely at certain points. Usually depending on the people going in and out of the nether. I'm hosting the game so when everyone logs out, mobs come back normally. It's weird because the disappear completely. We've tried resetting the mob spawning option and even putting the game in hard mode but it doesn't seem to do anything. Also, when there's only two of us, if we need something specific to spawn (like illagers at a tower) my friend needs to go into the nether for anything to spawn. When he goes back to the overworld, everything stops spawning at once. 

We're playing from different platforms (ps4, switch, iPad, etc)