I sent mine over to Sony to fix the very same issue. So far, it has been a few months and it hasn't begin ejecting my disk. *knocks on wood* My PS4 also had a beeping problem when it would shut off. Even when I removed the power cord from my PS4, it would still continue to beep. Idk if you have the same problem.
Mine started to beep like it wasn't properly shut down a few times, a couple of days before contacting Sony for the ejecting issue. Then, two days before the coffin got here it started to beep three times randomly while turned off. Maybe our systems were cousins.