Comment 4 for bug 1929209

Thanks for the log. There doesn't seem to be anything relevant there, at least not for the past few days. So it seems like the kernel isn't aware of the problem.

Indeed this looks like a bad cable or bad connection somewhere. Especially if fullscreening a window triggered the problem -- that suggests there's a bandwidth limit being exceeded, caused by a hardware problem. Most likely the cable or one of its connections, but there's a slim chance the monitor itself or even the laptop is faulty and unable to maintain a stable link at 4K 60Hz.

P.S. The monitor is not "a very popular Samsung one". It appears to be an Acer B326HK.