Sony Bravia MkV audio lag...

Ok so I have been lurking for a while, and have not been able to find the problem with my server. Whenever I play .MKV files, 720p, I get audio lag , and have to pause constantly. Does not happen with MPEG formats. I have a 46NX810, and it defaulted me to the 2010 Sony bravia profile. Is it possible that I should be using the 2011 or 2012 profile? Neither list my tv, but I am guessing 2010 is correct. Should I be using transcoding? I do not think it is my network speed, since I am using a gigabit router and was using my wireless, but I did test it with a wire and it still was happening! Any help or knowledge is appreciated !

[Illico]

That could be due to CPU load.
When you pause and wait some minutes, then restart, does audio still lag ?
You can enable detailled logging (see signature), restart serviio service, start the video and check the log file to find the ffmpeg command line used to transcode the file.
Then try loccaly in windows terminal the same command line and post ffmpeg log result here.