I have a weird, possibly related (?) problem recently on a Samsung TU7000.
It's hooked up to a computer, that shuts off video output after 30 minutes inactivity via windows power setting "Turn Off The Display", then shows "no signal" for roughly another 30 minutes then TV shuts itself off. There is no setting in the TV menu to do this at that interval, shortest sleep timer setting is 4 hrs.
I had no issue with it doing that, which it did fine for over a year, but recently, every 3 days or so with no changes I can recall, when TV is turned on, and PC already woken up, it can't see the PC's signal. It only does this when turned back on, never during use.
Rebooting the TV works (which until this point I didn't even realize you could do by holding the remote control power button for 5 seconds, and it reboots super-fast for a smart TV), -OR- unplugging the HDMI cable and plugging it back in sort of works except then it has shut off the Input Signal Plus, which I'm guessing reverts the HDMI to v1.4, so the 4K TV is in 30Hz refresh and 4:2:2 or 4:2:0, till I go into the TV menu to turn Input Signal Plus back on. I don't need to do that if I reboot it instead, just hadn't realized yet that rebooting is a better option until it worked.
I've fiddled with a few settings and so far can't replicate or solve it, since it doesn't happen every time. I tried another HDMI cable too, as the TV's test of HDMI recommended a different cable or lower resolution, but it had worked fine for over 2 years with that cable. Haven't had it running long enough with the new cable to see if that solved it.
I disabled audio playback sources over HDMI since I don't use the TV's audio, but that made no difference. I couldn't tell if you if it ever has HDMI audio problems because I've never used it long like that, but formerly it was doing HDMI audio fine over the same HDMI cable with a CATV set top box, which is no longer in use or connected.
It's the same video driver that worked for over a year w/o issue. I did not see any new firmware recently updated by the TV, but not too long before the problem started, I did see something strange, a popup to agree to Samsung's revised privacy terms. I suppose it is not outside the realm of possibility that the TV did update it's firmware without my noticing. I don't recall the prior firmware version # to check that. It shows it is running latest firmware ver 2601 (also this is the latest offered on their website) and the last version I had documented it running was 2505 in the fall of last year.
Ultimately one way or another, I think that at least some portion of the problem is due to a bug in the TV's firmware, in it not keeping Input Signal Plus turned on, unless it's turned off in the menu.
If it keeps happening, I'd wanted to try rolling back to 2505 but initial research suggests that you can't install an older firmware version on their TVs, so if all else fails then I'll check the website later to see if something newer than ver. 2601 is released.