Likely related to 23.976 with audio not 'timed' to sync (just a guess), but it's there. You're lucky not to have it with M3 as it's the same H/W as Q5 and Q10.
As much as I like my Q5, I'm on the fence about switching to Raspberry Pi2. Only things holding me back are: (1) converting all my 3D ISO's to MVC MKV's, and (2) the occasional sync issues I have with my BenQ W1070 projector (when trying to go back to Kodi UI after playing 3D). Losing ATMOS or the upcoming DTS:X is no biggie as I only have a 7.1 set-up (and Pi2 decodes HD audio and passes as LPCM to get full quality audio anyway).
On RPi2, no audio dropouts, no ghosting, great PQ (w/o any processing), perfect 23.976 and internal Kodi player.