System: Clevo P157SM (Sager NP8255-S).
I've just upgraded to Windows 10 Pro on my laptop and now the display refuses to turn off even if I lock the session or after the configured timeout (15 minutes on AC, 3 minutes on battery). It doesn't matter whether the laptop is plugged in.
The Monoff utility causes the screen to switch off, but it comes back on immediately, suggesting spurious input from an input device. Turning off the trackpad and disconnecting any external mice or keyboard do not help.
The laptop has a hotkey which switches off the display at the firmware level; a key press on the onboard keyboard turns it back on. The display stays off with this feature, eliminating the keyboard as a possible cause; however, it bypasses the OS and it doesn't allow any kind of ACPI control.
I have no trouble putting the computer to sleep—the system stays asleep unless I wake it up. The computer will wake up from external device inputs but ignores input from the onboard keyboard and trackpad (this is normal) so this eliminates external hardware as a possibility.
Any ideas on how to troubleshoot this?
Update: The issue seems to be caused by a userspace app as the monitor does turn off if left idle before I log into the machine. How do I isolate the guilty application?