I've been having the same problem lately, and only since the last two or 3 updates. Have you thought that the problem could actually have been a hardware or driver update, or Windows 10 OS update?
All of the sudden after a recent set of updates, powering on, and resuming from hibernate or sleep stops working and takes several times of holding down the power button to power on or resume activity.
It seems to occurs only when the keyboard is attached because every time I touch the detach button, the device seems to resume start up.
This is a serious issue. I chose this device because of the reputation of Microsoft Surface to deliver a top quality product. This truly seems to be a pattern among Microsoft Surface Book 2 users. It appears as if we are having the same issue it here and
it is either the hardware itself, or it is an update.