Instead of going to sleep mode, PC hangs with drive light on, have to press shut down button to turn it off.

It is this build specific bug, since it occurs in the same way with at least two users... Posted this before in news section, but could be easier to find here...

Looks like I resolved the issue. At least for now. Sleep works if I put it to sleep from start, and after selected time.

Run "powercfg /energy" command from admin command and save file energy report to desktop, so browser can read it..
There are other switches in powercfg, that can give you this info, too

You'll probably found that there were some errors with USB devices - check vendor IDs.
Install nirsoft USBdeview to check which are those USB devices (vendor ID would tell). In my case it turned out it was USB receiver for my wireless Logitech mouse and mouse itself.

Go to device manager and uninstall USB input device. Windows will reinstall that device, don't worry. After restart PC goes to sleep.

While in USBdeview, delete or disconnect latest USB flash drives.

This resolved my issue, but won't mark thread as solved yet. Let's wait if anybody else can confirm or give extra input...