This message may clarify the "It's a bug." issue.
The latest update for Apple TV may have been released a few weeks ago, but the notice for the update appeared on my device only 10 days ago - October 8th.
After the update installation, my problems with disappearing rental movies started.
I scheduled a call (October 10th) with a support person and explained the problem, and the eternally spinning gear when I selected "Check for Rentals". It was this support person who said, "There appears to be a glitch with the latest update." - his words, not mine. He then told me he was not surprised about the spinning gear and that I was not the only person with this problem; others with similar experiences had called. He didn't use the word 'bug', but 'glitch' comes pretty close. Perhaps he mispoke - I don't know. But he certainly created the impression that the problem was created by the latest Apple TV update.
As I reported in another post, he walked me through the steps that have fixed the problem for some people, but not others. Unfortunately, I fall into the latter category.