Why are chrome, safari and firefox rendering Open Sans 400 as Extrabold
Not sure if you got an answer to this question, but I had exactly the same issue myself. Didn't have Open Sans open in Suitcase and it wasn't in my System Folder BUT I did find Open Sans Extrabold installed in my Creative Cloud assets using Typekit. I removed it, restarted machine and problem solved. Hope that helps if you hadn't gotten to the bottom of it!