I just got an elgato 4ks today after having similar crackling/popping issues with the last capture card I tried (it was a rybozen, so I figured it was doing that because it was cheap), but having the same issues with this card. Seems like there's a few people having similar issues.
I managed to get the crackling to go down by changing the USB C port from the top of my computer to the back, but my OCD isn't gonna be satisfied until the issue's fixed. I recorded a clip showing some of the popping happening. I'm really hoping I can find a fix for this. I was hoping to be able to stream switch games in discord to my friends along with being able to easily play it on my computer so this seemed like the only option.
Also, I'm using the Elgato Studio to stream, though I do have OBS installed.
(redid the post to include better video)