Didn't I mentioned, "I believe"? I can't give the link but I have seen a guy in this forum with file from March call IRCC, and they told that the reviewing office said to review it again because of eligibility factors. "Reviewing it again means files go back to the queue, and hence it will take more time" (some agent told this in a youtube video). Also, I don't think that they didn't have touched the march files after so many months. Very weak files are rejected, strong are approved and files with some eligibility problems are kept on waiting.