Macbook Air external HDMI monitor randomly goes black - no signal

Hi all, this is nerve racking. Please help. I have been using my Samsung TV as an external HDMI monitor for my Macbook Air for several years. Without a problem. The connection is via a good thunderbolt/HDMI adapter. And suddenly, several days ago, this started happening:

When using the computer, suddenly the external monitor goes black saying that there is no signal. However, the computer still detects that something is connected and the resolution of the screen stays in the HDMI mode. So, there IS some communication between the two devices. When I disconnect the cable (on either end - the computer or the TV), the screen of the computer returns to normal. When I connect again, the screen goes to the HDMI mode. But the monitor still says that there is no signal.

This issue will happen randomly - after several seconds or after several minutes. Sometimes, the monitor comes back on. Sometimes not. This is all random.

The cable is fine and the monitor is fine - I tried with several other computers - macs and PCs. No problem. I tried other HDMI cables and also thunderbolt/HDMI adapters, even brand new ones.

The thunderbolt connector of my mac is also fine - I have another monitor with an old printer port and the mac sends signal through the the thunderbolt connector beautifully.

I tried manual display detection in System preferences. No change.

I reset the SMC of my mac. No change.

The max is always on, it does not go to sleep, it is always connected to power.

Restarting the TV or the mac, or unplugging the power of everything does not change anything.

This is like on supernatural thing... Seriously... This is like a human relationship. I feel as if the TV does not love my mac anymore. Technically, everything is the same but emotionally they do not connect anymore... :-)

If anyone has any idea, could you suggest something, please? Thank you so much!