[PROBLEM] No sound over HDMI 1360x768 but with 1280x720 it works

[jonpa]

Software
XBian version: XBian 1.0 (Knockout) (kernel: Linux 3.18.7+)
XBMC/Kodi version: Kodi 14.2-BETA2 Git:2015-02-18-04acf2f-dirty (Compiled: Feb 18 2015)
Overclock settings: default

Hardware
Device type and model (e.g. Raspberry Pi Model A/B 256/512 MB, CuBox-i i4Pro, ...): Raspberry Pi 2 1GB Model B
Power supply rating: 2.1A
SD card size and make/type: SanDisk MicroSDHC Ultra 16GB
Network (Ethernet or wireless): Ethernet
Connected devices (TV, USB, network storage, ...): Onkyo TX-SR605 via HDMI -> Samsung Plasma with 1360x768 resolution, Logitech BT keyboard via USB dongle,

Log files
Link to logfile(s): http://xbmclogs.com/pdimacuqa

Problem description:
When I set the resolution to 1360x768, which is the naitve resolution for my plasma screen, I get no sound over HDMI. I've tried all possible settings with pass through and such but no luck. No sound in the XBMC GUI neither.

If i set the resolution to 1280x720 the sound works perfect. Obviously I want to use the correct resolution so that my screen is in no need of scaling the output.

How to reproduce:
Change resolution to 1360x768