I have been having the same problem for about a week or two now, only on MKV video (AC3 audio). Tried changing audio to PCM without success. Tried to reinstall videostream plugin without success.
Windows 10 x64 / Chromecast 2 / Videostream premium

I have some videos (a small amount) that uses the segment linking ability offered by Matroska. Do you plan on supporting this in the future ? Not really a top priority obviously !