My bet is a mainboard and/or a power board failure. At this age plus it's only a 720p TV I suggest you not repair this. If you scan for channels how about an external tuner and connect the tuner via HDMI so the external tuner "fixes" that part of the problem?
Example at https://www.amazon.com/Converter-ViewTV-Recording-Function-Composite/dp/B01BO61CMS
There are many tuners like this that take an antenna input and HDMI out. Sorry but I don't sell or promote these so I can't answer much more but if I wanted a cheap fix, this might be it.
I have a LG 42LC7D TV, and it has been working pretty well except that it stopped being able to save the channels, and it had to search for channels every time it was turned on. We have a set top box from our cable company now, which takes care of saving the channels, so that doesn't matter now.
What does matter, though, is that whenever the TV is turned on now, it makes a noise -- similar to the sound of a VCR rewinding a tape -- for anywhere from a few seconds to a couple minutes, and then it goes away.
A couple days ago this rewinding sound was accompanied by the screen flashing like a strobe light slowly, but after about 30 seconds to a minute, everything was normal. The TV has not flashed when turned on since.
I have to say that one time several months ago, I turned on the TV and there was no sound. Turning the TV off and then on again fixed this problem, and we haven't had an issue since.
I wondered whether or not these things might be symptoms that the TV will eventually die, or whether or not these things are normal for LCD TVs. I know that these problems have not always existed. I think the rewind noise might have been happening for about a year or so.
Again -- the noise goes away after a little bit of being on. I think a couple days ago was the first time that I had seen the flashing, and it hasn't done the flashing since.
Anyone know what might be causing the problems, and what it might mean for my TV? Thanks.