Was this ever resolved? I am seeing the exact same thing with 13.0.2.5 using MKV H.265 profile - plays with audio only, no video
If I use an MKV H264 profile, the output plays fine. Also fine with MP4 H265. So my problem seems specific to the combination of MKV and H265.
I have not used DVDFab for about a year, but I did not have this problem using version 13.0.1.2.
Mauser
I don't think the problem you reported is the same as the problem in the thread. 
Anyway, please use mediainfo to analyze the MKV file that you don't have sound for playback and post the result. 
It'd be better to start a new thread for this problem. 
Thank you in advance.