Omega core styles suddenly go in the wrong order

I noticed that outline around contextual links regions disappeared. I started investigated the problem, comparing with another web site (which runs on the same omega codebase) and figured out that the difference in the order of omega styles how they appear in the page's HTML.

I attach the screenshot of this.

Any ideas how this could happen?

The styles must go in the opposite order: first — base and then — theme:

@import url(".../omega/omega/css/modules/contextual/contextual.base.css?n0sdma");
@import url(".../omega/omega/css/modules/contextual/contextual.theme.css?n0sdma");