I think i have found a reason,
Yesterday i tried 3 different cubes with 5 different Kore boards 
With using brand new Kore boards rev 1.4. A (which has a sticker on it, newly bought ones) current reading is -3,7A, and -3,9A
With using my old Kore boards rev 1.4.B (which i bought about 9 months ago) current reading is 0 and 0.1A
I think there is a problem on current reading of rev A Kore boards. Interesting part is that i bought these guys recently.