There is a bug in setGetVar. Bug occurs for links with '&' as entity (default value for $separator = '&'). PHP function    
parse_url works correctly only where ulr params are seprated by & not by entity. So this line is wrong

$parts = parse_url($uri);

befor that sholud be one of this lines:

$uri = str_replace('&', '&', $uri); or
$uri = str_replace($separator, '&', $uri);