So I'm finally getting around to testing this out, but I'm having difficulty finding out which components on the board are related generally to the sleep / wake functionality. I'm finding that U3900 has a lot of connected lines labeled with "WAKE" and "SLP", and I've also thought about checking out which components are in line with the lid angle sensor connector, but I'll admit I'm not very knowledgable in this area and it's difficult to find good resources online. Anyone able to educate me or point me in the right direction? Thank you!...

Thank you for the response! That's a great idea. Yep, got the boardview/schematics and equipment. I'll explore with a similar model and see if I can find a difference in readings. Thanks!...

If the lid is closed or the system is put into sleep mode for more than 30 minutes or so, then when I try to wake it back up by tapping a key or by tapping the power button I get no response. The device is warm but the CAPS lock light on the keyboard is unresponsive. To get it to reboot and be functional again I have to hold down the power button to force it to power off, then when I press the power button it reboots normally. I erased the system and reinstalled macOS to do a factory reset, and the issue still persists. I replaced the logic board and the issue is resolved with a separate known...