My problem is quite strange I couldn't find a source of the issue so I will just try to explain problem manifestation and hopefully someone will have an idea how to solve it (or just how can I start tracking the issue).
I have Thinkpad t460p and docking station ThinkPad Ultra Dock. I am running Ubuntu 16.04, kernel 4.4.0 with i3wm. When I plug laptop to docking station everything works fine I can set monitors as I like (using xrandr) and also suspend and wake laptop from sleep (while docked). Problem: if I undock laptop, it is then impossible to wake it up from sleep. Pressing power button turns the laptop on, but screen is always blank and it doesn't react to any inputs. Only way around it (as far as I can see) is to force reboot the laptop. Interesting thing is that undocking laptop while it is not suspended works until it gets suspended and after it encounters same issue. If the laptop was undocked while suspended it will also encounter same issue.
My question is, how can I address this problem, where can I find more information about what could be wrong, logs or any other hints what could be a problem.
One more observation: If i don't setup external monitor with xrandr unplugging laptop while awake works, as I can later wake it up from sleep, but in case of undocking it while encounter same issue.