I have 6 H/T sensors that have worked for several years. Recently the smart hub shut down. Checked voltage of PS and all was good. Powered down and up with no change. Powered down for 15 - 20 minutes and then powered up and smart hub worked. All sensors worked. But after short time hub shut down again. I can reproduce this over and over; un-plug, wait 20 min, plug in and use for 20-60 minutes, etc. What Can I do to keep hub up?