Hostile mobs don't spawn after upgrading from 18w16a

Playing in hard mode, locked, hostile mobs don't spawn. Tried /gamerule doMobSpawn true and changing the difficulty using the /difficulty tag. But nothing has worked thus far. Mob spawners still spawn mobs from what I've seen so far.

Update: Hostile mobs are spawning, just very seldom. Also, it seems like the mob cap is very low as I've only seen a max of five mobs spawn in at once. (four pigmen and one ghast.) I haven't been to the overworld yet since this discovery. I will update when I have more info.

Update 2: Overworld hostile mobs spawn, too. But also seldomly.