[bagofcrap24]

Simplest is to record a new shorter file and then check that it has the same issue.
Otherwise ffmpeg can be used for cutting down a file.

I recorded a short clip and uploaded it here. If I skip forward about 30s and then back 10s, the picture freezes whilst the audio plays and the picture stutters on the same frame for about 10s before unsticking.

https://drive.google.com/file/d/0B1fDI89...sp=sharing

I have been seeing this issue also.
Not with live TV or anything. Just NFS playback of an h264 mkv.
I cannot reproduce the issue with OMX acceleration enabled. Only with mmal.
The method of reproduction is the same as you have described.
Skipped 30s forward a few times (I.e skipping opening credits)
(Went to far) so skipped back 30 seconds.
Audio will continue to play but video is stuck for about 20 seconds. The odd frame update will occur during this time.
There was nothing shown in the debug log but the only thing I noticed was that the kodi.bin CPU usage was at 100%.

It's not 100% guaranteed to happen which also doesn't help finding the cause