Live Stream with music video sputtering

Hi all! New to the forum. I need help! I’m currently a musician who can’t tour because of the pandemic. I do a weekly live stream. Because my piano player is in a different country, we make videos of our performances and I stream them, live on fb. I am experiencing sputtering on the videos with the music but not the videos with us chatting! I don’t understand what is happening. I have the music videos at 720, same as chats. Please help.