This question already has an answer here:
When I follow a direct link to an answer (a share link, or I click an "answered 1h ago" or "modified 1h ago" link in the active questions list), the sticky top bar will cover up the top of the answer, including the upvote button. Here's a direct answer link for you to test it yourself.
Here's what I see after following a direct link on one of my sites:
... then I scroll up by the height of the sticky top bar to see the actual top of the answer:
This isn't even a site-specific thing, since it will happen right here on meta: