
If you use "Help | View activity log" and look at the its last logged event(s) before you restarted the PC, it will probably show you the last thing that Hauptwerk did before the hang occurred. For example, perhaps it was trying to start or stop MIDI, and some particular MIDI driver (or audio) was hanging (e.g. perhaps because the hardware or USB connection to its MIDI or audio device had been dropped for some reason, such as a USB device having gone to sleep).
In case it's relevant, here's an excerpt from the Hauptwerk user guide that covers how to prevent Windows putting USB ports to sleep:
... on Windows 10 you would use 'Windows Control Panel | System | Power and sleep | Additional power settings', select the 'High performance' power plan, then click its 'Change plan settings | Change advanced power settings', then make sure that the settings are set as follows:
Sleep: Hibernate after = Never (for 'plugged in' if present)
USB settings: USB selective suspend setting = Disabled (for 'plugged in' if present)