The chance of a crash with Fullscreen when ALT+TAB is common to others as well. The game engine just hates it.
Currently it looks like the crash can be more related to Fullscreen ALT+TAB or/and XACT3DApply. If a bot would go around hard freeze people's PC by crashing the entire game, there would be many more bells and whistle.
Windows Event Log:
Using the Start Menu:
Click on the "Start" button or press the Windows key on your keyboard.
Type "Event Viewer" and press Enter.
Check Application and System events if any Supreme Commander related crashes are available.
Alternate:
Using the Run dialog:
Press Win + R on your keyboard to open the Run dialog.
Type "eventvwr.msc" and press Enter.
Example for visualizing:
a7092cc4-9c24-45fc-ac8e-add7eb33c3ad-image.png