It wasn't a surround sound system, we were watching on the built-in app on a Fire TV from the TV's speakers.

Also just Google "malcolm in the middle missing audio" and you'll find a ton of people with the issue

https://www.reddit.com/r/malcolminthemiddle/comments/1kggg7d...

This also reminded me of another issue - the show was filmed to be broadcast in 4:3 but apparently someone along the line decided 16:9 is inherently better, so they put out the show in widescreen and now there's a ton of shots where you can see things you're not supposed to see. Someone else standing in for an actor that wasn't there when they filmed, or a toy doll in place of a real baby because they filmed on a day the baby actor wasn't there.