I had a mob farm that after updating to the snapshot 18w43c randomly wont spawn mobs, I last used it in 1.13.2 so it could be any of the snapshots. It is in a Cold Ocean Biome but used to work fine until I recently used it after updating and nothing spawned and the entity count kept saying 0/1, I haven't changed anything on where the mobs spawn so I assume it is a snapshot bug but I don't know what is causing it. The mob farm's spawning area is mainly cobblestone and is 2 blocks tall of space for each floor.
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Thanks and I just noticed that the one in my redstone world works almost perfectly but only during the day with around 1 mob dropped a second on average and gets nothing at night. The one in my survival still doesn't spawn a single mob with the entity count saying 0/1 during the day. Could the cold oceans be glitched with mob spawns not working?
Most likely caused by MC-138189.