I have a new 75" Q90T and I am so far pretty happy with it, with just one exception:
I get intermittent picture drops where the TV shows the circle in the middle and then switches to the "no signal detected" screen. Sometimes the picture just drops to a black screen for 1 sec and then returns, while the audio via the receiver continues.
TV is connected via HDMI (eARC port) to a new Denon 2700X - multiple devices are connected to the Denon (UHD player, media box, PS4). Problem happens with all devices so I think the culprit is the TV (I had the same problem with my older Denon 2000X connected to the Q90T, setup never had problems with my old Sony TV).
HDMI cable from the receiver to the TV was already switched and replaced with a HDMI2.1 compliant cable.
Anybody seen a similar effect? It is hard to pinpoint as it (thankfully) only happens once in a while but it is annoying nonetheless...
I am experiencing the EXACT issue with my Samsung qn55q80t. I am also connected to a Denon receiver, model ARV-X6700. I removed the receiver from the mix. Connected things directly to the TV...ie the Amazon Fire Qube, or the Nvidia Shield. Or a Tivo Premire. I will try your suggestion mentioned below to see if it works. I hope it works, I'm getting tired of this issue.
The reboot (as I described) did the trick for me - hasn't happened since (also there have been two firmware updates for the TV since then, not sure if they changed something there as well).
I just recently had this 1 sec dropout issue with a Samsung Q50R. The reboot seemed too easy a trick to actually work, but so far after an all night gaming session, no dropouts (fingers crossed).
Wanted to thank you for your post because I couldn't find this solution anywhere else on the Internet!
I could be watching something, source doesn't matter, Tivo, Nvidia Shield, FireTVCube, and out of the blue, picture goes black, spinning circle, while this is happening I notice the Denon AVR-6700x display shows output channels dropped, then come back, then you might hear sound first then the image starts playing again on the display. It happens daily sometimes several times while watching something. Other times it doesn't. No rhyme or reason. It does happen more often when changing source input. All my sources go through the Denon, so one output to the TV. Sometimes TV times out and gives you the blue screen saying no source. I can clear it by changing the input on the Denon to something I know always has output like the Tivo. Wait for the TV to sync up then switch back to whatever the source was I wanted to begin with. I'm at a loss. I know people are reporting this issue out there. But nothing from Samsung other than reset the TV. I'm hoping for a firmware update that changes how the TV senses video input. I believe the issue is a bug with that portion of the code. Maybe delay what they do today and stay on target longer. I believe the TV senses something and immediately goes into this search for input mode instead of just staying there for a while longer and maybe totally avoiding what is happening. Just my opinion.
My picture dropouts didn't return so far (fingers crossed) - and they happened while connecting via a Denon AVR or directly to the TV, so it was definitely the TV.
As for the "Input Source" - I would call this the most annoying "feature" of this TV (or of any TV I have ever owned). The insistence of the machine to switch inputs on its own when it "thinks" it doesn't get a signal.
Insert a 4K disc that requires a bit more loading time... TV gives you the circle and then the "no signal message on HDMI1". All the stuff is connected to HDMI3 (the eARC port), so why the TV would switch to another port - that has no connected device at all - is fully beyond me.