Part title font of weirdness

[samjegal]

Before part active

After part active

My env is eclipse mars and below

[renataogarcia]

I had a similar problem because of the custom CSS I had to change the font of the tabs. Replacing it with the one below solved my issue:

CTabItem {
    font-size: 10;
    font-weight: normal;
    font-family: "Ubuntu Light";
 }