I installed Win10 x64 from a bootable USB 2.0 stick using one front USB Port of my case. Everything worked well and I went on installing latest drivers from Asrock/AMD homepages.
After a few hours I noticed that my front USB-Ports (1x USB 3.0, 1x USB 2.0) aren't working as expected. I tested them with several devices (WLAN stick, USB stick, external HDD, ...).
Sometimes I see them in Windows Device Manager and they work correctly (can access external HDD...).
But, sometimes when I plug in a device, nothing happens. There's no change in Device Manager and also no corresponding message in the Windows Event Log. The same device consistently works on the rear mainboard USB ports.
When a device is not recognized on the front USB ports, I reboot to UEFI, and see the hardware working (e.g. external HDD), so I don't think it is a loose contact for the front USB port of my case.
I also can't imagine this is a driver problem because, ever since Win 8.1, the USB drivers are included from Microsoft.
How may I troubleshoot this further to isolate the problem?