Fonts Not Accurately Rendering in Preview/Publish

I'm experiencing an interesting quirk where Open Sans font weights are rendering differently when editing the slides than it does when it's previewed or published.

When editing a slide the normal and bold font weights appear correctly:

When the module is previewed or published, however, the bolded text maintains the kerning but reverts to the normal font weight:

Has anyone experienced this? Any suggestions to the cause (and hopefully a solution)?