The laptop is a recent Dell XPS 15z and the problem is as follows (reproducible about 90% of tries):
- put laptop to sleep using either Start->Sleep or closing the lid
- laptop goes to sleep after about 5 seconds, but instantly wakes again showing a black screen (touching the keyboard or moving the mouse shows the login screen one normally gets after wake)
- login again, put laptop to sleep
- latop stays in sleep mode
powercfg -lastwake after the first instant wake shows the audio controller is responsible. Why would that be, why only the first try, and how to fix this?
Wake History Count - 1 Wake History  Wake Source Count - 1 Wake Source  Type: Device Instance Path: PCI\VEN_8086&DEV_1C20&SUBSYS_04461028&REV_05\3&11583659&0&D8 Friendly Name: Description: High Definition Audio Controller Manufacturer: Microsoft