This is the command that I used:
/give @p minecraft:stick 1 0 {Unbreakable:1,ench:[{id:0,lvl:225},{id:1,lvl:225},{id:2,lvl:2525},{id:3,lvl:225},{id:4,lvl:225},{id:5,lvl:255},{id:6,lvl:255},{id:7,lvl:255},{id:8,lvl:255},{id:16,lvl:255},{id:17,lvl:255},{id:18,lvl:255},{id:19,lvl:1},{id:20,lvl:255},{id:21,lvl:255},{id:32,lvl:255},{id:35,lvl:255},{id:48,lvl:255},{id:49,lvl:255},{id:50,lvl:255},{id:51,lvl:255},{id:61,lvl:255},{id:62,lvl:255}]}What I expected to happen was to get the drops that I deserved. When I am almost on top of the animal that I kill, I get all of the drops, but when I'm just a few blocks away and then run to get the drops, some of them disappear.
Steps:
1. Get a command block.
2. copy and paste this command into it:
/give @p minecraft:stick 1 0 {Unbreakable:1,ench:[{id:0,lvl:225},{id:1,lvl:225},{id:2,lvl:2525},{id:3,lvl:225},{id:4,lvl:225},{id:5,lvl:255},{id:6,lvl:255},{id:7,lvl:255},{id:8,lvl:255},{id:16,lvl:255},{id:17,lvl:255},{id:18,lvl:255},{id:19,lvl:1},{id:20,lvl:255},{id:21,lvl:255},{id:32,lvl:255},{id:35,lvl:255},{id:48,lvl:255},{id:49,lvl:255},{id:50,lvl:255},{id:51,lvl:255},{id:61,lvl:255},{id:62,lvl:255}]}3. Find an animal (Pig for example) and stand as close as possible to it and kill it. Look to see how much meat you got, write the number down.
4. Next find another animal, and with the same stick you got from the command, kill it, except stand 4 blocks away. After you see the drops, wait a few seconds and some will disappear.
So, from what i'm understanding, you're killing an monster/animal with a stick that has a very high amount of looting enchantment level. This increases the amount of drops you get from killing stuff, but it is also very randomized! That's why you're getting "less" when you try it a couple times. Just the randomness of the looting enchantment.
Now, for the "items disappearing" part: When there's more than 1 of the same item on the ground, and they're close enough together they will merge into one and be a stack of items, but they will still have the correct amount of items in that stack. This is to prevent lag, in larger case scenario's you could have 10 stacks of items on the floor, which would result in 640 entities, if they weren't stacked together. Hope this is understandable 🙂
I hope this is what you're experiencing. If it is, then this is not a bug!