Freeze when playing mkv

Upgraded recently to Kodi 17, using Aeon Madnox skin.
On occasion when playing an mkv movie (all my files are mkv) the movie will freeze for about 10 seconds and then go back to the main menu. I can then select the movie again and start playing and it doesn’t seem to happen again on that play through.

I have been now trying to grab a debug log but of course it doesn’t happen when I have that on…eventually I will capture it.
Any thoughts on this issue? Has anyone else seen this?

Home built HTPC
Windows 7 SP1

Dual attached NAS with GB connection

Thanks