I updated my M8S+ (S905x) device with the 8.2.5 release.
I have a problem with some mkv files. For instance, here you can find a 30sec sample.
I tried with older version of LibreElec (an old adamg 1.0.6 release) and also the latest CoreElec. All have the same problem: video stuttering and audio out of sync.
The file is reproduced perfectly with Kodi (X86), VLC and other desktop player.