On the 8.x-1.x branch, for the rate.vote and rate.undo_vote routes there's a 500 error if the entity doesn't exist.
Error: Call to a member function bundle() on null in Drupal\rate\RateVote->vote() (line 112 of /app/web/modules/contrib/rate/src/RateVote.php)
It's not likely users will stumble into this accidentally, but Google Search Console noticed after some nodes were deleted.
Go to /rate/node/[ID]/updown/-1/yesno or similar where the [ID] is for a node that doesn't exist.
A 404 error should be thrown instead.
Closed: won't fix
1.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.