External monitor disconnecting & reconnecting randomly.

Hi ya'll,

I'm having connection issues with my external monitor that basically prevent me from doing my work as a designer. It's been going on since February and I'm getting desperate.

I have a 2019 fully specced MBP, and a LG Ultrafine 5k Display that have been working fine since I bought the macbook in november 2019. This february I upgraded to Big Sur, and literally a day or so later I started getting these ridiculous random disconnects/reconnects.

What happens (see the attached video):

https://www.youtube.com/watch?v=nwecZD7HoH8

It disconnects my monitor that's attached through USB-C for about 2-3 seconds and then reconnects again. Once this starts happening it usually does not stop un till I pull the USB C cable out and let is rest for a few minutes. The frequency once it starts disconnecting differs, but has been getting worse by the week.. From a reconnect every few minutes to literally reconnecting every 5-10 seconds..

But when I pull the cable and let it rest, it's also possible for it not to occur for hours (usually not the case).

It mainly happens during calls through teams / hangouts / zoom. And CPU demanding tasks. I replicated it with playing a game as well. But lately it can just happen without any reason. Browsing the internet can be enough to set it off. And like I said.. once it starts going, it keeps going.

I've had countless hours of contact with customer support.

-I did all the PRAM VRAM resets.

-I rolled back to Catalina

-I ran diagnostic tools that were then sent to engineers.. they saw kernal panics but couldn't explain them

-I reinstalled fresh and transferred files through Migration assistent.

-I reinstalled and didn't transfer anything (lost all my apps and settings basically)

-I bought a new Apple USB C cable.

None of the above worked. It feels like after updating to Big Sur something internally got fried, and it doesn't matter if I go back, it's still happening.

I went to the Apple store 3 times. They did put it on their monitor for 48 hours and "Stress tested" it, without any success in finding an issue. I even went there and sat there for two hours with my monitor and laptop to replicate the issue.. but without success.. (like I mentioned before, sometimes I get lucky and it does not happen for hours.. too bad it was in the apple store).

So working is basically impossible because of the random disconnects. And I'm seriously getting desperate since I've tried EVERYTHING.

The only option I still have is buying a new monitor to see if that's the issue, but to me that feels like overkill to fix a problem that literally started 1 day after upgrading an OS. Store employees told me they think it's the motherboard, but they're not willing to take it in for repair until they're able to replicate it through their stress testing.

Is there anyone that knows how to fix this, or what I should do next?

Thanks.