Is my external USB drive causing erratic sleep/hibernate behaviour?

I've been reading up around sleep settings as I keep finding my Late 2012 Mac Mini in a weird hung state each morning that requires a force-reboot (it's like running Windows 10 years ago!) I thought the "deep sleep" function was to blame but when I ran pmset-g I got this: System-wide power settings: Currently in use: standby 0 Sleep On Power Button 1 womp 1 autorestart 0 hibernatefile /var/vm/sleepimage powernap 0 networkoversleep 0 disksleep 10 sleep 60 autopoweroffdelay 14400 hibernatemode 0 autopoweroff 1 ttyskeepawake 1 displaysleep 10 standbydelay 4200 However https://apple.stackexchange.com/questions/113954/difference-between-autopoweroff-and-standby-in-pmset says: > With the release of the OS X Mountain Lion v10.8.2 supplemental update > 2.0, a new feature was introduced to enter safe sleep after four hours of the computer being connected to AC power. This is an effort to > comply with the European Energy Standards (ErP Lot6). **This will only > occur if there is no wireless or Ethernet activity and no activity > from external devices such as USB storage devices**. I have an external USB hard-drive as the 2nd drive on my SSD MacMini as my main data drive. If this is turned off, I recently noticed the system won't boot (folder with a question mark) which seems odd for an ancillary drive. Either way, would the presence of this drive prevent deep-sleep/hibernate/standby? - It will sleep a couple of hours fine, it's only overnight it has issues - It generally still has lights on my connected USB mini-hub when it is frozen - It typically "semi-wakes"; the screen recognises an active input and typically I get a black screen with a responsive mouse cursor I started writing a totally different question but then was thinking whether my USB drive might be a culprit here or I should be looking elsewhere? How can I tell if the Mac is is sleeping Vs standby Vs hibernate Vs deep-sleep to track down which transition or action is causing the problem?