When a query string is provided to the BuildLink function, when SES URLs are being used, the code tries to determine if a forward slash needs to be added to the arguments.LinkTo value, but instead of checking the linkTo value for a trailing forward slash, it is checking arguments.queryString (requestContext.cfc line 823), which is almost guaranteed to never have a trailing forward slash and thus will always add the forward slash to the LinkTo value, producing a double forward slash if the linkTo value already ends with one.

this issue goes back to Feb 8, 2011 when the same problem was addressed.