UR44C Not responding

Hi there,
i’m having problems with my UR44C on a new AudioNetworx i9 PC. Sometimes i get neither input nor output from it, although Windows says that the device is connected and working properly. I haven’t found a reliable way to trigger this error yet, but when he appears, i’m really stuck. Plugging out and in won’t help, reboot neither. Removing from device manager / uninstall / reinstall seems to help - at least sometimes.
When this happens the dspMixFx-App shows three dashes (’—’) as version numbers for ‘Boot’ and ‘Main’ (see attached pic). The device is flashed with newest firmware, all drivers are up to date. Does someone have a glue what might be the problem here?