Heads stacking incorrectly.

1. Make a command block with this command

   /entitydata @e[type=Item,dy=1] {}

2. Throw a head on the command block.

3. Activate the command block.

4. Copy the output in it.

5. Repeat 2-4 with the other head.

6. Post the outputs here.

as well as the commands used to make the heads (the summon)

/summon Skeleton ~ ~1 ~ {CustomName:"Bonesplitter Scout",CustomNameVisible:1,ArmorItems:[{id:leather_boots,Count:1,tag:{display:{color:4653056}}},{id:leather_leggings,Count:1,tag:{display:{color:4653056}}},{id:leather_chestplate,Count:1,tag:{display:{color:4653056}}},{id:skull,Damage:3,Count:1,tag:{display:{Name:"Orc Skull",Lore:[The head of an Orc]},SkullOwner:chayseboi24}}],HandItems:[{id:bow,Count:1,tag:{ench:[{id:48,lvl:1},{id:49,lvl:1}]}},{id:stone_axe,Count:1}],ArmorDropChances:[0.0F,0.0F,0.0F,1.0F],HandDropChances:[0.0F,0.0F],Attributes:[{Name:generic.maxHealth,Base:20}],PersistenceRequired:1}

Here is the summon used.

In response to SunCat:
first test:

[19:37:21] The data tag did not change: {Motion:[0:1.5824100265939025E-20d,1:-0.0d,2:-5.547105165038869E-21d],UUIDLeast:-5262989687309559405L,Health:5s,Invulnerable:0b,Air:300s,OnGround:1b,Dimension:0,PortalCooldown:0,Rotation:[0:285.14404f,1:0.0f],Thrower:"fracerman",FallDistance:0.0f,Item:{id:"minecraft:skull",Count:1b,tag:{SkullOwner:{Id:"e712743c-e063-4174-b0e3-2607fc391e47",Properties:{textures:[0:{Signature:"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",Value:"eyJ0aW1lc3RhbXAiOjE0NTg4NzI0MTI2NjEsInByb2ZpbGVJZCI6ImU3MTI3NDNjZTA2MzQxNzRiMGUzMjYwN2ZjMzkxZTQ3IiwicHJvZmlsZU5hbWUiOiJjaGF5c2Vib2kyNCIsInNpZ25hdHVyZVJlcXVpcmVkIjp0cnVlLCJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvZTI2YmRkNTVhYWU5NTM1NTc4OGNjZDEzZjZmMDFjMWY4MTUwNWQ1NzYxNTM1Y2I1ZjliYTQ3MGJkMTU4N2Y3IiwibWV0YWRhdGEiOnsibW9kZWwiOiJzbGltIn19fX0="}]},Name:"chayseboi24"},display:{Lore:[0:"The head of an Orc"],Name:"Orc Skull"}},Damage:3s},UUIDMost:4220461836036622374L,Pos:[0:145.99002381689698d,1:6.0d,2:1000.1594410282656d],PickupDelay:0s,Fire:-1s,Age:92s}

second test:

[19:38:30] The data tag did not change: {Motion:[0:3.83777614174198E-13d,1:-0.0d,2:-8.58567989507671E-14d],UUIDLeast:-5466077394096877708L,Health:5s,Invulnerable:0b,Air:300s,OnGround:1b,Dimension:0,PortalCooldown:0,Rotation:[0:231.61879f,1:0.0f],Thrower:"fracerman",FallDistance:0.0f,Item:{id:"minecraft:skull",Count:1b,tag:{SkullOwner:{Id:"e712743c-e063-4174-b0e3-2607fc391e47",Properties:{textures:[0:{Signature:"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",Value:"eyJ0aW1lc3RhbXAiOjE0NTg4Njk1MDkwMTIsInByb2ZpbGVJZCI6ImU3MTI3NDNjZTA2MzQxNzRiMGUzMjYwN2ZjMzkxZTQ3IiwicHJvZmlsZU5hbWUiOiJjaGF5c2Vib2kyNCIsInNpZ25hdHVyZVJlcXVpcmVkIjp0cnVlLCJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvZTI2YmRkNTVhYWU5NTM1NTc4OGNjZDEzZjZmMDFjMWY4MTUwNWQ1NzYxNTM1Y2I1ZjliYTQ3MGJkMTU4N2Y3IiwibWV0YWRhdGEiOnsibW9kZWwiOiJzbGltIn19fX0="}]},Name:"chayseboi24"},display:{Lore:[0:"The head of an Orc"],Name:"Orc Skull"}},Damage:3s},UUIDMost:4051566748518533180L,Pos:[0:145.5072023097701d,1:6.0d,2:1000.4890200994591d],PickupDelay:0s,Fire:-1s,Age:59s}

third test :

[19:39:42] The data tag did not change: {Motion:[0:3.3881351659306543E-15d,1:-0.0d,2:-1.7961394049049858E-15d],UUIDLeast:-5949394273938387345L,Health:5s,Invulnerable:0b,Air:300s,OnGround:1b,Dimension:0,PortalCooldown:0,Rotation:[0:119.5463f,1:0.0f],Thrower:"fracerman",FallDistance:0.0f,Item:{id:"minecraft:skull",Count:1b,tag:{SkullOwner:{Id:"e712743c-e063-4174-b0e3-2607fc391e47",Properties:{textures:[0:{Signature:"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",Value:"eyJ0aW1lc3RhbXAiOjE0NTg4NzI0MTI2NjEsInByb2ZpbGVJZCI6ImU3MTI3NDNjZTA2MzQxNzRiMGUzMjYwN2ZjMzkxZTQ3IiwicHJvZmlsZU5hbWUiOiJjaGF5c2Vib2kyNCIsInNpZ25hdHVyZVJlcXVpcmVkIjp0cnVlLCJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvZTI2YmRkNTVhYWU5NTM1NTc4OGNjZDEzZjZmMDFjMWY4MTUwNWQ1NzYxNTM1Y2I1ZjliYTQ3MGJkMTU4N2Y3IiwibWV0YWRhdGEiOnsibW9kZWwiOiJzbGltIn19fX0="}]},Name:"chayseboi24"},display:{Lore:[0:"The head of an Orc"],Name:"Orc Skull"}},Damage:3s},UUIDMost:-1406091659124455789L,Pos:[0:145.59334349118055d,1:6.0d,2:1000.4577846931677d],PickupDelay:0s,Fire:-1s,Age:63s}

fourth test:

[19:40:27] The data tag did not change: {Motion:[0:1.053705743171645E-15d,1:-0.0d,2:-4.014652202007572E-17d],UUIDLeast:-6325521487001969847L,Health:5s,Invulnerable:0b,Air:300s,OnGround:1b,Dimension:0,PortalCooldown:0,Rotation:[0:253.74677f,1:0.0f],Thrower:"fracerman",FallDistance:0.0f,Item:{id:"minecraft:skull",Count:1b,tag:{SkullOwner:{Id:"e712743c-e063-4174-b0e3-2607fc391e47",Properties:{textures:[0:{Signature:"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",Value:"eyJ0aW1lc3RhbXAiOjE0NTg4Njk1MDkwMTIsInByb2ZpbGVJZCI6ImU3MTI3NDNjZTA2MzQxNzRiMGUzMjYwN2ZjMzkxZTQ3IiwicHJvZmlsZU5hbWUiOiJjaGF5c2Vib2kyNCIsInNpZ25hdHVyZVJlcXVpcmVkIjp0cnVlLCJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvZTI2YmRkNTVhYWU5NTM1NTc4OGNjZDEzZjZmMDFjMWY4MTUwNWQ1NzYxNTM1Y2I1ZjliYTQ3MGJkMTU4N2Y3IiwibWV0YWRhdGEiOnsibW9kZWwiOiJzbGltIn19fX0="}]},Name:"chayseboi24"},display:{Lore:[0:"The head of an Orc"],Name:"Orc Skull"}},Damage:3s},UUIDMost:-8301957484781549722L,Pos:[0:145.64070870541042d,1:6.0d,2:1000.4698201921842d],PickupDelay:0s,Fire:-1s,Age:64s}

The signature doesn't have the same value, fix: copy the skullowner tag from the tests and replace the summon command one with it

I tried to copy the skull owner tag from the tests and input them into the skull owner portion of the command. This dosent seem to work, instead the mob just spawns with a Steve head and not the orc head it should have.

Copy this:

SkullOwner:{Id:"e712743c-e063-4174-b0e3-2607fc391e47",Properties:{textures:[0:{Signature:"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",Value:"eyJ0aW1lc3RhbXAiOjE0NTg4NzI0MTI2NjEsInByb2ZpbGVJZCI6ImU3MTI3NDNjZTA2MzQxNzRiMGUzMjYwN2ZjMzkxZTQ3IiwicHJvZmlsZU5hbWUiOiJjaGF5c2Vib2kyNCIsInNpZ25hdHVyZVJlcXVpcmVkIjp0cnVlLCJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvZTI2YmRkNTVhYWU5NTM1NTc4OGNjZDEzZjZmMDFjMWY4MTUwNWQ1NzYxNTM1Y2I1ZjliYTQ3MGJkMTU4N2Y3IiwibWV0YWRhdGEiOnsibW9kZWwiOiJzbGltIn19fX0="}]},Name:"chayseboi24"}

And replace

SkullOwner:chayseboi24

Okay, the command works and sucessfully spawns in a scout with the correct head and it stacks, as do the others. But here is the question that I will let you know, if I leave the head in a chest travel somewhere else, wait a while then obtain a new one will they stack with the old? I will update that shortly. Thanks for your help!

Alright this is seemingly resolved for now... Thanks a ton, so if I wanted to create another skull that always stacks would I simply create it then replace the skull owner with the extra long command and all that jazz?

Yep. The texture Signature is updated with a skin update, and MC thinks the texture different from the old ones, so the heads are different and don't stack. If you say what texture to use, the heads will always stack.

Related problem in 18w20c. Whenever i try to place a player_head{SkullOwner:Playername} (In this case, i tested using my own head) in a chest, it seems like it stacked until i exit the chest instance. Then the head i just placed will pop out of the chest.

To replicate,  do, ./give @p player_head{Skull_Owner:playername}. and put it in a chest. Then do the same thing with the same player's head. Put the second head in the same spot in the chest and it should pop out upon closing it.