Just never fell asleep. It's just misfortune after another in this attempt, but the log looks so far like this:
Nap 1: 10 min sleep (?)
Nap 2: 30 min sleep
Nap 3: 2 h 30 min sleep
Nap 4: 0 min sleep
3h 10 minutes seems decent enough. I'm not feeling that tired now, but I'll expect to be zombified in few hours. My body obviously still thinks nap 3 as a night time sleep so it makes everything it can to prevent me from getting up. I just have to excert more discipline at the third and fourth nap. Also I need to get to bed a bit earlier if I'm not feeling very tired like happened just on this nap. When I'm in a hurry to fall asleep, it just never happens. Need some time to relax.
On first attempt I got to 2.2 when I finally completely overslept, now that shouldn't be such a big of a trouble. Improving seems probable, but that is not saying much.