The only other way sperm (from semen or precum) can leak through a condom is if there's a hole or tear in it. Things that can make a condom.
Back in 2011, John Stamos played the perp in an episode of Law & Order: SVU called “Bang.” His damage: poking holes in his condoms before.
American and imported condom manufacturers electronically test every condom for holes and other defects. They also conduct additional.