How to fix my video lag that occurs on every possible video source on my Dell XPS13 9350 on Windows 10?

I have a video issue: Whenever I play video, no matter the source (youtube, netflix, netflix app, a downloaded video file), the video lags the audio. This seems to build up as I play a video: it gets worse and is very apparent within minutes or even within the minute. Pausing the video sometimes seems to ‘reset’ the problem, but it will very soon be very obvious again. I am working on a Dell XPS13 9350 (2015), and Windows 10 Home. Knowing nearly nothing about such issues, my guess is that this is a graphics-related issue. The problem has been around for a few months now and a few weeks ago I had a graphics-driver update. I hoped this would solve the problem, but it didn’t. I know this laptop doesn’t have the best graphics-specs, but I can’t imagine it is just not capable (anymore) of properly playing video? What could be the problem and how do I solve it?