It seems like when you have only one empty bucket in a slot and you interact with snow powder, water or lava, the bucket disappears. When you fill up a bucket with milk from a cow or a goat it works normally.

Similarly, when you try to place a bucket of lava, snow powder or water, the content of the bucket will be placed but the bucket itself will disappear.

I should point out that when you have more that one empty bucket in a slot, filling it up will give you the bucket with the content as intended. The bug seems to only occurs in hardcore and survival mode (in creative mode the bucket stays the same way whatever you do so it makes sense).

The bug also happens when you try to release whatever creature in a bucket, like fish or axolotl.

Steps to Reproduce:

1. Get yourself an empty bucket.
2. Try to fill them with anything but milk in survival mode - You should lose the bucket.
3. Try the same thing with more than one empty bucket in a single slot - It should work as intended until you have only one bucket left.
4. Get yourself a bucket filled with everything but milk.
5. Try to place it in survival mode - The content of the bucket should be placed but the bucket will disappear.