The armor stand has multiple sections in it where the art goes unused.
Attached is the current texture with the unused sections selected in Aseprite, the texture in block bench (which to note, does not include everything the vanilla texture includes such as the credits), and the proposed fix.
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In 1.18.2 and 22w15a.
Can confirm in 1.19.
You missed a couple of them that correspond to the left part of the highlighted body element in block bench, at the top of the texture file.
I've attached armor stand unused pixels.png
to highlight these as well.

Can confirm in 1.19.3 and 23w03a
Good job! I think this is not really a bug. A simple flaw that does not affect the gameplay.