Bug in play since 1.21.9, affects all versions since.
Reproduceable a few ways, mainly by separating items off from a stack to the side and quickly double clicking to return the stack to the chest. Doing that will return even the items you separated out, when it should not.
This is very hard to name and explain, please see attached video.
Thank you for your report!
We're tracking this issue in MC-301852, so this ticket is being resolved and linked as a duplicate.
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