I have a keyboard and DVD drive connected to the USB ports on my LG Ultrafine 5K display, then the display is connected to my 2020 Intel MacBook Pro via Thunderbolt.
Occasionally, when I plug in the MBP into the monitor, the monitor comes on but none of the USB devices work. The LG’s built-in webcam will also not work, I presume it’s on the same USB bus as everything else.
When I reboot, everything works fine. I’ve tried an SMC reset several times, eventually the problem comes back again. Has anyone else noticed this behavior?