So the answer is that Windows 10 is automatically changing the display scaling whenever connected to a new monitor (be it a projector or TV). Windows detects the recommended setting for the monitor it is connected to and is changing it. To fix the problem you have to change the scaling back to 100%, apply, log out of Windows, and log back in - THEN the scaling will "stick".

Adagio will not properly launch unless the scaling is at 100%.