Today, I finished reviewing 40 items in the Suggested Edits queue at Stack Overflow, and switched to the First Posts queue. There was a question that I tried to edit, but it already had a pending suggested edit by another user. It redirected me to that user's suggested edit, but I could not edit the post as I was already out of my daily limit.
I suspect this is a bug. Either don't allow me to review posts with pending suggested edits if I've exceeded my limit, or temporarily increase the limit by one to allow this particular review.