Subtitles from mkv videos missing

On a Windows 10 environment. All my videos have been ripped (MakeMKV) with the english subtitles enabled. They are all mkv videos. I upgraded from 16.1 to 17 RC3 and the subtitles would show only occasionally. Rather strange. I upgrade to RC4 and now they don’t show at all. The subtitles worked fine with 16.1 and earlier versions of Kodi as well with VLC. I’ve tried turning them off and on in Kodi but no difference. Any ideas?