This may be an issue others are not seeing because of the content of their CSS but I noticed something...
Both the single quote (apostrophy) and regular quote are getting escaped improperly.
For instance if I put this in my custom CSS:
font-family: "Times New Roman", Times, serif ;
The custom.css file contains:
font-family: \"Times New Roman\", Times, serif ;
Not a huge error but it does cause issues, especially in URLs such as:
The font-family issue is important because if the font name contains whitespace it must be in quotes.