People hate change. And even now, IPv6 support in new devices can be hit-or-miss. Even most cellular networks in my country don’t support IPv6.

I’d start with checking logs with journalctl as a privileged user. If the device disappears, there should be logs about it. Maybe that will point the way.

From West to East: Not the usual road traveled

It would be worth looking through your journal. There is usually some amount of logging even in the event of a hardware issue. See journalctl.

As others suggest, does sound related to sleep / suspend. If that is the case, you could have a problem like I did where my motherboard BIOS incorrectly reports usb capabilities which results in an immediate resume from sleep. That abrupt change causes the amdgpu driver to crash, and the system hangs soon after. My workaround is to disable features on the offending usb host controller.