So update for anyone who might be interested :

I discovered that it was game dependent.

So far, the scan lines only occurs in the Ghostrunner game and when i launch the moving photo test "alien invasion" on testufo.com at 240 pixels/sec in full resolution.

It might be an optical artifact due to the framerate. 

Not game dependent for me. Even comes and goes when using the desktop.

Dell just replaced the monitor for me, I thought it was going well, now it suddenly just started happening again.

Occurs on multiple computers, on two monitors Dell has sent out (same manufacturing month).

Any suggestions?

Hello

Not game dependent for me anymore too, I was wrong :

- It was nearly systematic in Ghost Runner and appeared in Death Stranding too, in dark environements.

- It was on desktop too.

Try (if not already done...) to set the refresh rate to 144 Hz via the windows settings. For me it canceled the scanlines on desktop, but it still come and goes in games.

Turning the monitor off and on can sometimes make the lines disappear for an unknown amount of time.

Hello

Same problem for me with a GTX 1070 and 2 differents S3422DWG. I tried many configurations in the OSD and the Nvidia Control Panel(g-sync, custom res and sync...) but the lines are still visible on moving pictures. My GC works pretty well on other monitor (Xiaomi 34, Asus VG34...)

Setting the color to YCbCr instead of RVG seems to reduce the problem on desktop only. 

I noticed some artefact in Explorer too. Files'name are yellow and white in dark mode

and with the test below  https://www.testufo.com/inversion 

I'am out of ideas...

Hey guys, I am seeing the same issue too. I reached out to Dell and they sent me a replacement and it's happening on that one too. Both were manufactured in May 2021.

What's really interesting is I managed to do a screen recording of me moving the cursor around on a certain Amazon page that will trigger the vertical lines. Playing that video at full resolution (full screen) will also trigger the vertical lines and it's very reproducible. 

Since I haven't sent back the original monitor yet, I hooked it up to my laptop and played the video on that. The video triggers the vertical lines there too. So for me, the issue is highly reproducible on both (desktop+replacement monitor) and (laptop+original monitor) using the cables that Dell provided in the box.

I thought that it may be Windows messing up and the lines were captured as part of the video clip, but I don't have another 3440x1440 to test... [edit] I am not convinced the lines were recorded as part of the video because as the video is playing, I see the lines over the mouse cursor which isn't part of the video.

Have you guys made any progress on this since the last post?

I just bought this monitor in less than a week, huge disappointment. So what should I do? If I send it back I get an other faulty one like IgnitedX? Sometimes it comes up, sometimes it doesn't. Mine works ok on desktop and had no issues with a late XP era PC. If I turn off / remove the DP cable / turn on-off "premium" freesync sometimes it gets back to good. Sometimes it just doesn't care. At this point I have no idea what causes it. I get it like 90% of times in Doom Eternal, Skyrim SE with vsync only seems to be unaffected (had it with all the other stull turned on- enhanced synck, freesync), No Mans Sky seems to be OK, though it used to has it as well. I have no idea what actually causes it.

DELL, tell us something!

I haven't been gaming much on mine, but this screen capture in Windows desktop triggers the issue for me every single time across different computers with HDMI and DP. Maybe you can try playing this clip to see if it triggers the lines on yours too? Make sure you play it in full screen "4K", lower resolution doesn't seem to trigger it. 

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

I have been chatting with them over email and trying a bunch of different things - no luck so far. 

Hi,

We’re still awaiting an update from our internal team. Rest assured, we are constantly tracking this and will write to you as soon as we hear from them.

I think its due to the pattern on the page...

Check out this page at http://www.techmind.org/lcd/index.html

See some of the tests and watch it instantly appear!

Haha, yep, exact same effect for me. I find just hovering over the image (to show the magnified view) is enough to trigger it.

I got one monitor (May 21). Dell replaced it with another monitor from May 21. Still the exact same problem. Sigh.