When working on the theme I accidentally introduced an error by putting a square bracket in one of the lines, like the one we can see in line 92 here:

This did not raise any errors on TrueChange allowing me to publish the theme and break all the classes that were below that line. 

Since the theme was visible in the sources of the browser and properly loaded, it took too much time to realize it was a simple syntax error. This could have been avoided if TrueChange would not allow to publish CSS with syntax errors.