Weaver Xtreme V 6.2.1.3 shoud fix the stray CSS code or other random characters being displayed has been fixed.
The root cause was the CSS minifier that minified the generated the cached CSS for the various options.
This was compounded by the fact that the cached CSS would only be cleared if the admin actually saved the option settings which is not necessarily a part updating a theme. (The theme will now update the cache as needed.)
The 6.2.1.3 version fixes a issue with the CSS cache notification to the Legacy settings interface.