Screen does not always turn off according to Power & sleep settings

DESCRIPTION

Please advise, I am trying to solve this puzzle.. Basically screen wont always turn off according to the settings set in Power & sleep. Sleep, on the other hand, works.
Sometimes monitor will turn off correctly after a set time, say if I set a minute or two just to test then it works. But 15 minutes never work. Sometimes if I change additional power settings back and forth it starts to work, but only until next restart.
I can't find a solution nor cause of this problem. Windows 7 power settings worked correctly.

SYSTEM INFO

Windows 10 is cleanly installed on HDD in UEFI mode and I am using/testing it only for a few days yet. Slow ring updates. No additional USB devices are connected except keyboard and mouse. PC is quite new, Skylake based (i5 6600, Asus Z170M-PLUS, R9 390).

THINGS I HAVE TRIED AND RESULTS

• Clean boot and Safe mode - same.
• Updating BIOS - same.
• Disabling USB selective suspend - same.
• Booting without mouse - same.
• Testing for wake armed devices with powercfg and disabling LAN adapter wake - same.
• Using USB 3 instead of USB 2 to connect mouse & keyboard - nothing.

"Some" results:

• Generating powercfg /energy report. Report shows error "USB Suspend:USB Device not Entering Selective Suspend". Windows 7 did not show such error (hardware switch dual boot, easy to compare).
• Disconnecting and reconnecting mouse while system is on - display turns off correctly after, but only until next restart..
• Switching Power plans back and forth - again, starts to work, until next restart.