Solved! Toshiba M50-A-118 doesn't shutdown or sleep

Dear tomshardware community,

I have a Toshiba Satellite laptop that can't properly shut down or sleep/hibernate (restart is fine).

What happens, frequently after some hours of usage, is that uppon asking the PC to shutdown/sleep, it will try to do so and then the screen goes black. But the LEDs of the power button, battery indicators and WLAN are kept on (the CPU fan keeps on spinning as well).


What I have tried already:

-Fresh Intall of Windows 10 Education
-Disabling Hybrid Sleep a.k.a. Fast Startup (in power options)
-Disabling Hibernation (in cmd)
-Running CHKDSK (in cmd)
-Replace original HDD to SSD

-Flashing a new BIOS version (couldn't do it because I already have the latest version)

Interestingly, when I replaced the HDD to SSD and made a Windows 10 fresh install, the shutdown was fine. After the automatic upgrade to Windows 10 Education Upgrade (which brings Fast Startup), the problem comes again.

Specs:

Toshiba Satellite M50-A-118 PSKPNE
Intel core i5-4200U
Nvidia Geforce GT740M
6 GB Ram
240 GB Kingston SSD

Windows 10 Education 64-bit Upgrade