Certain mobs can't drop loot

As I've played through the snapshots the past week, I've noticed something that really hurts the game. Certain mobs aren't dropping loot, even some on the mobs that have a 100% drop rate aren't dropping anything: after testing a bit, these are the mobs that are still dropping their normal things

• Skeleton
• Sheep
• Cod
• Salmon
• Tropical Fish
• Pufferfish
• Ravager
• Wither Skeleton
• Shulker
• Wither Boss
• Iron Golem
• Snow Golem
• Panda

While all of these mobs are dropping xp, some mobs, like Evokers and Chickens, which normally have a 100% drop rate on certain items, aren't dropping those respective items (Totem of Undying, Raw Chicken). This affects Blazes and Enderman, and this prevents people from getting to the end.