Hello here as well I thought we could look at the playback issue together:
I have a Cubox i4pro that worked wonders with OpenElec. Up until Kodi 16.1 (OE 6.95.3), playback was always flawless and I never had any issues with the thing (apart from some HDMI colour depth stuff that was fixed with kernel 3.14). These new Krypton alpha builds however look nice, have more features, but have issues with video playback. Under exactly the same circumstances (everything stays the same, same device, same movie, same network - I simply switch SD cards), Kodi 16.1 plays everything smooth while Kodi 17 sometimes struggles with even SD content.
Here is a debug log from 17: Kodi 17 Cubox-i4pro IMX6 playback - Pastebin.com
And here is the same from 16.1: Kodi 16 Cubox-i4 IMX6 working - Pastebin.com
(just saw your .007-sr3.14 image, will test that and provide logs here)
Any idea what goes wrong here? I'm happy to provide more logs if that helps.