You're replacing the Location header with just fqdn.com. The browser assumes that means it should make a new GET request to it's current host/URL + fqdn.com. If they'd requested http://www.example.com/path, they'd make a new request to http://www.example.com/path/fqdn.com which isn't what you want.
Can you try Nitass's suggestion and reply back with what you find?
HTTP::header replace Location "[string map -nocase [list inside1.net fqdn.com inside2.net fqdn.com] [HTTP::header value Location]]"
If this doesn't work, can you log the new location header value and describe what request the client makes and the server's response?
log local0. "New Location: [HTTP::header replace Location]"
Aaron
Nimbostratus
