I also tried to activate quickboot.
After 4 hours of endless reboot, i looked closer what happening.
With a camera and rewind, it is possible to read clearly the status between each reboot :
Optimizing app…
4/145
20/192
19/192
17/192
15/192
15/192
4/146
16/192
17/192
13/192
15/192
16/192
…
11/192
20/192
…not very encouraging and a bit weird.
Finally, I did not want to let my FP2 rebooting all night and let it overheating (after more than four hours, it was already very hot).
So I did a hard reset (which erases all data) to recover my phone.
My advice : DON’T try to activate currently the quickbook !
For Fairphone devs, i have the logcat of the last bootloop. Ask me on PM if you want a copy.