My TCL 75R615 has been performing flawlessly since I purchased it 3 months ago.
I have it set to default to the HDMI/ARC input so upon start up, it displays my satellite TV broadcast (that's going through an AVR).
For the past few mornings when I turn it on, I notice the status indicator continues to give a slow pulsing blink for about 30-60 seconds after the TV appears to be fully booted and performing normally. I'd just assumed it was updating software or an app. Nothing else seems abnormal while the light is pulsing. After it does this, I've occasionally checked the update screen, and the last update remains August 8 12:08 am. It indicates the last check was just a couple minutes after I turned on the TV, so I assume it checks every time it's powered up. I've never paid attention to this previously.
This morning, when I turned it on, it did not do the prolonged slow blinking, but turned on as usual and began displaying the satellite broadcast like usual. Then after a few seconds, the screen went black followed by the TCL red logo screen. It stayed on this screen for several seconds and acted like it was rebooting. It then appropriately went to the correct input and began displaying the satellite image like usual. Once again, the last update remains August 8 12:08 am, and the last check was this morning. I will note the uptime says 4 minutes. (I don't know if that resets every time the TV is power cycled or if it's supposed to correspond to the firmware version life. I've not paid attention to this previously.)
I'm assuming what happened this morning is that the TV rebooted, but I don't know why.
All my settings were retained including picture settings.