XPS 13 9343 Going to sleep/hibernation after 30 seconds

Hi all,

I'm having a strange issue with my XPS 13 (9343, FHD screen, i5 5300U).

It is going to sleep/hibernation ~30 seconds after I lock my account in Windows (Win + L) even though I've set Windows to not sleep at all, even when on battery.

Why I am unsure if it's sleep or hibernation is because the power button is not on at all, but I can at the same time resume the machine by moving the wireless external mouse.

The first thing I did with this machine was to format the disk, install Windows 8.1 Enterprise x64 and add it to our domain.

Thought this issue was related to Windows 8.1 (after living with this issue for 8 months) so I've just reformatted the disk and installed Windows 10 Enterprise (1511 edition)... and the issue is still present [:'(]

I can't find anything in the BIOS that seems to be related to this issue. I did find one setting about C3 state, I changed it for enabled to disabled but it did not seem to change anything.

Anybody got any ideas?

Regards
P-H, Sweden