I have already a Karaoke on .ASS with effects, when I drag the .ass subtitle to the video player works perfect.

But when I mux the MKV with the .ass subtitle the karaoke do not see properly, and I never had this problem before.

I'm using MPC player.

But is rare, when I have sub and mkv separated the subtitle effects looks fine, but when I mux works bad.

How can I fix this?

Thanks