Unfortunately, there doesn't seem to be a simple fix for this. Even after my post above yours, mine started to do it again after a few weeks. It appears to be an issue with the drivers. What i have found is that it only does this when the laptop is in sleep mode. The power button on the dock works to put the laptop to sleep and will wake it if not undocked. However, if i undock the laptop and dock it back, it will not wake it. I have to open the lid (which i set to power on when opened) to wake it from sleep. When the laptop is powered off completed, the power button on the dock works every time to power it on. That's what leads me to believe it's a driver issue. Since this appears to have been an issue for a few years for zbooks in general and HP docks, it doesn't seem to be on their priority list or list at all to resolve. I mean, they replaced my board 2 times to try and fix it instead... There is a recent firmware released for the dock this past week i haven't done yet, but will do it this week and update this post to let you know if that resolved it for me.
