Hi again Daan v,
You're overriding by changing the class OSInline which is used in many places.
You should be more detailed on your CSS to avoid collateral effects.
In your case, like .testDisplayBlock.OSInline {display: block;}.
In this way the CSS would only apply to an element which has both classes and since it is more specific it should have priority over the others.
Cheers,
João