Why did some of the delegates refuse to sign the constitution? social studies weekly 17?

They believed that there were flaws that needed to be addressed

This included both big issues like whether or not the bill of rights should be introduced as well, down to smaller issues that were a matter of technicality or were not really issues at all to begin with. Some people didn't want to sign it even after the amends, but it wasn't a big deal since it eventually got ratified and became the constitution.