Edit: looks like I'm actually able to reproduce the reboot as many times as I want. I open the gallery, open a video (with mx player free) then I go back and start scrolling; the display locks again and start fading away. Attaching the second kmsg. I have 500+ in my gallery, taken with many different cameras.
Edit2: indeed, I'm able to reproduce this. It happens every time. Attaching a third and last kmsg.