So, I have a System76 Lemur Pro 9 laptop, running Ubuntu 22.04. I have a Lenovo USB-C dock connected, and a Sceptre C35 monitor plugged in via HDMI (though the behavior is the same if I use DisplayPort). I've been using this setup with no problems for 3-4 years.
This morning, I needed to work on an iOS application, so I plugged a Macbook Air into the dock via USB-C.
After using the dock/monitor with the Mac, my Lemur Pro is now unable to use the monitor reliably. If I plug it in, it will work at first, but after a few minutes (duration is random, usually less than 5 minutes, sometimes only seconds), my Lemur Pro will play the "hardware disconnect" sound and the monitor will go black.
When it gets in this state, unplugging the laptop from the dock and plugging it back in will not resolve it. The only way to resolve it is to unplug the laptop, unplug the dock from AC power, plug the dock back into AC power, and then plug the laptop back in. After I do that, it will work for a few more minutes, before disconnecting again.
I've looked through various log files, but don't see any smoking guns...
From /var/log/syslog:
Aug 31 10:10:51 system76-pc NetworkManager[627]: <info> [1693491051.0492] device (enx482ae3b4472c): state change: unavailable -> unmanaged (reason 'removed', sys-iface-state: 'removed')
Aug 31 10:10:51 system76-pc kernel: [ 652.978286] usb 2-2: USB disconnect, device number 5
Aug 31 10:10:51 system76-pc kernel: [ 652.978294] usb 2-2.1: USB disconnect, device number 7
Aug 31 10:10:51 system76-pc kernel: [ 652.978434] r8152 2-2.1:1.0 enx482ae3b4472c: Stop submitting intr, status -108
Aug 31 10:10:51 system76-pc kernel: [ 653.043110] usb 2-2.3: USB disconnect, device number 6
Aug 31 10:10:51 system76-pc /usr/libexec/gdm-x-session[2195]: (II) intel(0): Disabled output DP1-2
Aug 31 10:10:51 system76-pc /usr/libexec/gdm-x-session[2195]: (II) intel(0): Disabled output DP1-3
Aug 31 10:10:51 system76-pc rtkit-daemon[1120]: Supervising 12 threads of 5 processes of 1 users.
Aug 31 10:10:51 system76-pc rtkit-daemon[1120]: message repeated 3 times: [ Supervising 12 threads of 5 processes of 1 users.]
Aug 31 10:10:51 system76-pc rtkit-daemon[1120]: Successfully made thread 8635 of process 8399 owned by '1000' RT at priority 10.
Aug 31 10:10:51 system76-pc rtkit-daemon[1120]: Supervising 13 threads of 6 processes of 1 users.
Aug 31 10:10:52 system76-pc rtkit-daemon[1120]: message repeated 2 times: [ Supervising 13 threads of 6 processes of 1 users.]
Aug 31 10:10:52 system76-pc /usr/libexec/gdm-x-session[2195]: (II) intel(0): resizing framebuffer to 1920x1080
Aug 31 10:10:52 system76-pc /usr/libexec/gdm-x-session[2195]: (II) intel(0): Disabled output DP1-1
This makes it seem like some kind of virtual USB device internal to the dock has disconnected from my system, but I don't know why...
Can anybody recommend any further troubleshooting steps?
