Describe the Bug

I was filling the Shulker with Spawn Eggs from this mod: https://modrinth.com/mod/villager-pickup

The capacity bar is still empty:

Steps to Reproduce

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Expected Behavior

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Screenshots

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Fabric Version

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Mod Version

Latest 1.21

Log Output

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Additional Context

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Thanks for the bug report :)

A quick note on how capacities are calculated, so we're on the same page while trying to work this out. Capacities are calculated based off the maximum number of items a shulker can hold. An empty shulker (of normal size) can hold up to 64 * 27 = 1728 items. A shulker holding a single pickaxe would instead have 64 * 26 + 1 = 1665, since the single stack limit of the pickaxe decreases the maximum number.

Do those eggs stack to more than 1, like vanilla eggs? If that's the case, it should appear empty because 47 is significantly smaller than the maximum capacity.

They store with the mod unique entity data, they can't stack.

They can stack, they are just vanilla spawn eggs with extra NBT on them. If 2 villagers have identical NBT their eggs will stack.