Andrew:  OK, he had time to look at it anyway yet today.  It loads here UNDER CONDITIONS. The secret is "marker" files.  The first time you load the .mkv file you sent, it creates in $HOME/.bcast5 the filename.idx (index file) and filename.mkr (marker file).  GG added code a long time ago to make this work by creating marker files as .mkv files are recalcitrant sometimes.  The "marker" file is a crutch because ffmpeg does not make it work.  So the first time you load the file you sent, it does not work; the second time you load the file now that the index AND marker files exist you can see the picons/thumbnails on the timeline.  For marker files to be created, you must have in Settings->Preferences, the Interface tab, "build ffmpeg marker indexes" checked/enabled.