Screen flickering or cutting out for a few seconds?

A buddy of mine is running an old RTX 30 xx—honestly, he can’t even remember the exact model 😁—hooked up via DisplayPort to a 4K monitor. The issue is that his screen occasionally just cuts out entirely... it's rare, maybe once a day, where everything goes black for about two or three seconds before flickering back to life. This has been happening consistently for nearly two years now, ever since he first paired this card with the monitor.
Does anyone have any insight into what the typical culprits might be here? We don't exactly have a spare DisplayPort cable on hand to run a quick test right now...

You might want to grab another DisplayPort cable just to rule out a faulty connection...