I've got the too many reservations error when trying to add a recording.
I fitted a smart plug socket (Tapo TP-Link) a few weeks ago. It is set to turn off the power to the TV in the early hours of Monday and Friday mornings for 1.5 hours. I have had none of these problems since.
I have the same problem (too many reservations error) when trying to add a recording and have also tried switching off/factory reset/firmware update actions to no avail.
My model : UE40MU6470UXXU