I have a small deck that gives me the occasional reviews. Today I cleared out the first of two and decided to hibernate the last item in the review using the action button hibernated the last card. The toast notification said there was an error with the request, the remaining card count decremented to 0, and the item itself stayed visible with the input box with no way to “finish” the session normally aside from the results button. In a second tab I was able to verify using the card manager that the item did actually get hibernated.
I tried it again with a different deck and had the same issues.