[eXistenZ]

It's correct, stand-by using sleep cover or power button leaves light at the right %, powering off moves it to 1%.

My problem is that also de/activating the night mode moves light to 1%, for instance i have light on at 2%, long pressing light button turns off the light then activates Night Mode, at this point I press the light button again to turn on the light, but this doesn't appen because it's moved to 1%.

EDIT: It's not the long press to change the light % to 1, every pression on the light button resets it, has nothing to do with night mode, sorry

The solution is to manually change the value of FrontLightLevel= in .kobo/Kobo/Kobo eReader.conf from 1 to 2 ore whatever you like.