uicommons just got released to 2.13.0. The changes include one possible breaking change: the path that uicommons CSS uses to refer to fonts has changed (see commit).
I checked the change in a few parts of the Reference Application and it looked like it was a no-op. However, if on upgrading to uicommons 2.13.0 you find that your fonts and icons are suddenly broken, this may be the culprit.