Why do some guys interact with, then avoid a woman, when they're not on bad terms?

There's this demeanour in a guy that gives me the feeling he's rather annoyed by my presence. Sometimes when we're on opposite sides of the room, he'll make funny faces at me and it's alright. Yet, whenever we're sat next to the other, he'll always switch places or ask someone else to take his spot and then ignores me for the rest of the day. This happens especially right after we had some interaction.

He's always first to help others. Whereas he'll give me feedback on something I'm doing wrong/could do better and then proceeds to tell someone else to work on that with me, rather than doing it himself (even when he's not necessarily doing anything else).

Our interactions are often rather physical, but only ever briefly (a fist bump, hand on shoulder, or he'll randomly grab my hand) and honestly, nothing more than just a short greeting. Last week he bumped into my shoulder, walked away and then ignored me the rest of the day. It wasn't meant to be hurtful, but definitely on purpose.

I might be exaggerating, but it is thoroughly confusing to me.
Like... why not just leave me alone if you don't want to be in my presence?
Why do some guys interact with, then avoid a woman, when they're not on bad terms?
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