Issue with strings 20 and 25

Well frankly I don't regret "how it works" because hats off we managed to resolve our issues so the next time I have a problem I'll come back to this THANK YOU

Hello
I could be wrong, but this issue seems like a badly "tuned" channel
or not "exactly on the right channel," if you understand better
hence the sound distortion

if you're receiving via a rooftop antenna, check the antenna amplifier (it might be a bit underpowered)
if you're using an indoor antenna, it's even worse
if you're using a TV box (from your operator) check the HDMI cable (it can make a difference if it's a budget cable) or ensure that the scart plug is properly inserted.
I was advised to change the amplifier in anticipation of the initial switch to DTT (in SD back then) and the technician took the opportunity to go on the roof for the installation of a satellite dish to change that amplifier, telling me that the power of the old one would be a bit limited for DTT
right or wrong? Nevertheless, everything works perfectly, in all weather (especially in strong winds, I live in Brittany not far from the ocean)
and it works really well,
which wasn't the case with my immediate neighbor, who never wanted to pay for it, and had the same type of amplifier that dated from the same era but eventually suffered from poor reception or recurrent "no signal" after the switch to DTT.
so question of power? or oxidation of the old amplifier? or something else, who knows

re
no panic either
the transmitters are still conducting tests, delegating such a signal to another transmitter, retrieving the signal from yet another one, etc.
until the moment when everything will be permanently set up for April.
after switching to HD you will need to scan for channels again, and you will see if the problem disappears or not.
if not, it will be time to check with your local antenna technician whether your antenna needs to be realigned, or if the amplifier needs to be changed, or any other solution that will be proposed to you, because you will likely not be the only one.

however, if they tell you at that moment, "we are not aware of any problems like that.." then I don’t know
maybe it’s the tuner in your LG, acting up, not sensitive enough, or too sensitive? I don’t know but we need to wait for now.
by the way, what model is your TV? so I can check?

I also have an LG, and the sound from channels 20, 21, and 25 has been resonating for the past few weeks now.
I don't have a signal amplifier, and I have a rooftop antenna. It used to work fine, but for the past few weeks, channel 25 has been resonating, and after a channel scan, I got channels 20 and 21 that started to resonate. I hope it's not an issue with LG TVs and that it's related to tests for HD digital terrestrial television.
My TV: LG 42LD550

re
well, it's the same as above, Kevin
antenna hidden under the roof or no antenna amplifier on the aerial, or the amplifier is too old...
all of this causes a loss of reception power for the signal, or can slightly distort it
wait for the transmitters to balance each other out (after April 5th), then perform an auto scan or a manual search (fine tuning) on the problematic channels
if there's no improvement, it might be LG, I don't know because I chose Samsung :)

Same resonance issue on the 1, the 23, the 24... and LG TV everything went back to normal by disabling audio description. Thank you very much.