[SOLVED] Option Spin down HDD in Kodi not working on Rpi3

[Roy Terhaar]

Software
XBian version: XBian 1.0 (knockout) (kernel: 4.4.6+)
XBMC/Kodi version: 16.0 Git:2016-03-11-a3eb4fa
Overclock settings: none (default installation settings)

Hardware
Device type and model: RPi3
Power supply rating: Standard original Rpi power supply
SD card size and make/type: 16GB
Network (Ethernet or wireless): KODI configured to use Ethernet
Connected devices (TV, USB, network storage, ...): Yamaha RX-773 receiver (to TV), 2 harddisks on USB ports Hitachi 2GB, Seagate 4Gb.

Log files
Link to logfile(s): -

Problem description:
Concerns the option 'Spin down HDD' (System -> Xbian -> XBMC)
If this option is ticked (enabled) and the confirmation question to save the setting is confirmed,
the system displays the messgae that the setting is saved, but it is not saved.
Also the two HDD's are not actually spinning down as well.
After re-entering the same menu option (also after reboot) the option shows unticked (disabled).

The spin down option did work previously in my same setup using Rpi B+ which I have now replaced with the Rpi3.

How to reproduce:
As in problem description, I can reproduce this issue.