I have based my experince on those MKV files I have had problems with so your experince may vary depending on the files you are trying to play.
Obviously. Still you’re the first one complaining about out of sync MKVs so I really doubt it’s a firmware bug.
You misunderstood what I was saying. I had jitter problem with a few MKVs on my WDTV Live and SamsungTV. I put that down to WDTV not liking the way they were encoded and/or muxed as they played fine with other players. Trying to solve the problem I remuxing those files with Mkvmerge but that caused the a/v to go out of sync over time. I wasn’t saying that was a WDTV firmware problem and I wasn’t complaining either! I just stated an observation. The problem was also visible in VLC on my computer. I was saying that that was not a way to solve MY jitter problem!