Users of Fast Secure Contact Form and JetPack have been reporting the redirect is broken after the form is posted.
A new version of Fast Secure Contact Form is ready to test. I just need a couple testers.
I just want to make sure the problem is resolved with JetPack.
Since I do not use JetPack I am not able to test them myself.
If anybody can test it with JetPack. Contact me here and I can email you 4 PHP files to upload to your plugins/si-contact-form. folder. The problem should be fixed and you can tell me if so.
Fast Secure Contact Form plugin author