drawers not fitting flush in dresser

I have at least one dresser drawer component(Haverty's Marseille collection) that my son broke when he climbed on it trying to reach the top of the dresser. I have determined that I need a Kenlin 32-076 drawer case runner - one of mine is definitely broken. I cannot find any other drawer pieces that need replacing, however, several other drawers are not fitting flush into the dresser. Can you offer any advice on troubleshooting what I can do to figure out what's wrong and ultimately fix this? I'm so glad I found your site and have needed to address this issue for a long time! Many thanks for your help!