This has been happening for the last month or so. When I turn it off the blue light stays on and the device becomes unresponsive. I have to turn it off using the switch on the back and back on again. It doesn’t happen every time but seems to be getting more frequent.
I have tried a level 2 maintenance mode reset to no avail.
I have now solved the problem. It was related to the Logitech Harmony remote I use. I also would like to go back to a T2100. I don't have a 4K TV so apart from the extra storage there is no benefit and I have to put up with the noisy fan.