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I have a ThinkPad T480s laptop connected to a Dell P3222QE 32" 4K monitor via USB-C. I only use the external monitor and have disabled the laptop screen. I use 4k at 60 Hz and run Ubuntu 22.04.

Around 10 times per day I get issues with the connection. Things that happens are:

  • The screen goes black for 1-3 s but the image return.
  • The screen disconnects and Ubuntu falls back to the laptop screen. Disconnecting and reconnecting the cable often fixes this. Sometimes after reconnecting the external monitor goes to 30 Hz with no option to change to 60 Hz. Then I need to reconnect it at second time.
  • A few times both the external screen and laptop screen have gone black and a reconnect was needed.

I tried both with Wayland and X.org - with same issue.

What can this be? How can I troubleshoot it?

it is very annoying when you are in the middle of coding.

user1595349
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  • I found this googling for the same, exact issue. I've a Dell XPS, but the rest of the config is the same as yours. Also see here: https://forums.developer.nvidia.com/t/external-monitor-issue-on-ubuntu-22-04-jammy-using-nvidia-510-and-470-proprietary-drivers/214152 – Dr. Gianluigi Zane Zanettini May 23 '22 at 08:39
  • Experiencing the same on openSUSE 15.4 (Kernel 5.14.21-150400.24.28-default). I don't think it is (only) connected with the graphics: when I connect wired Ethernet through USB-C adapter I also get really frequent disconnects. Sometimes disconnect is long enough to kick me out of Microsoft Teams ongoing call. – Andrei Sinitson Nov 12 '22 at 10:24
  • Searched a bit more and it seems that the problems are across different devices (USB-C hubs seem to make not difference for the better), manufacturers and also affects Windows. There are plenty of similar threads, here is one example: https://www.dell.com/community/Monitors/U3419W-unstable-USB-Type-C-connection/td-p/7759612 Feels a bit like under-baked hardware/firmware combination. Sadly there is no alternative, since new laptops come with USB-C ports only. – Andrei Sinitson Nov 12 '22 at 10:49

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