Yeah, sorry about that. I wanted to check the most common problems we see when your TV works fine, but totally ignores you pushing the power button.
We're dealing with either a bad micro or bad power going to the micro.
If you weren't pressing any buttons on your remote or TV front panel, and you saw that flashing, I would have suspected a bad button making constant contact on your remote or the TV set. But that's not the symptoms you described.
So I'm looking at the fact the TV does work fine a lot of the time, but not 100% of the time. It's telling me your micro isn't starting up.
Think of it like this. You ever have days you start up your computer and it doesn't boot up correctly? Then you have to shut it down and restart it to make it work? Your TV is behaving about the same way, and checking to see if the SD card slot being used has ever occurred previous to this problem. I've had a couple lock up the TV set like your's is.
I think I better check and see if you want to repair your own TV set, or if you'd prefer to leave that responsibility to an electronic engineer. While your problem revolves around a 5 volt power supply that runs your micro, and we need to test that with a digital voltmeter, it may not be something you are comfortable with.
So I think I may need to get a better understanding of what you want to do at this point in time.