I'm finding that this and other streaming services do this with .mkv videos. They are squished. VLC player can stream now but it is a bit glitchy. I hope Videostream can fix the aspect ratio glitch with mkv files soon.
I'm having the same issue. I'm using a Mac with OS High Sierra 10.13.5 using Chrome version 67.0.3396.99 (offial build) (64-bit). I just installed the download (while typing this out) and it fixed everything, thank you!!