Hostile mobs fail to appear, but can deal damage to the player. Potentially immune to damage (couldn't see it, didn't hear it take damage-- may have not been hitting it)
No problems with passives (yet)
Similar bug reported on Xbox One, where any mobs (and items) hostile or passive would dissapear close to the player.
The key difference is they never appear in the first place, it spawns invisible from what i've noticed.
I have this same issue on Nintendo switch. Hostile mobs spawn invisible but can deal damage. They cannot be hit. Has happened with blazes, wither skeletons and drowned for me.