Chains cannot craft chainmail armor or repair chainmail armor in anvil

those items are not related. This is a feature request

isnt a bug. Request here: https://feedback.minecraft.net/hc/en-us

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All armor can be crafted except chainmail armor, and chainmail armor seem can be crafted by chains.

It would make sense, but this is a feature request that belongs to the minecraft feedback site.

Here is link to that: Posts – Minecraft Feedback