I have a problem with sound lags some times for a second and some time many times in a movie, I am use this SPDIF module here:
https://www.raspberrypi.org/forums/viewtopic.php?f=100&t=93522
And I upgrated to the newest OSMC version.
Here is the log so hope anyone can help me with fixing this problem 
I stream Movies from my Synology NAS DS1515+
http://paste.osmc.io/odefayepat.vhdl
I have tried both with wifi and cable, but still the same.
Can you be more specific with the problem.
Are you saying audio gradually gets out of sync with video?
Does it start in sync and get worse? Does seeking help?
If you switch audio from spdif to analogue or hdmi do you have the same problem?
I dont think the audio get out of sync with the movie, but I just stops for a sec then It comes again, and it do that alot some times, I cant test the HDMI because Its on a projector
You can enable analogue and plug headphones in can’t you?
This isn’t a solution but a test to narrow down where the problem is.