Just updated with latest FSCF version.
I have mine setup to redirect to the same page (#) after sending a mail.
In the latest version, after the first mail is sent, successfully, it does redirect back. No problem, redirect message also shows.
Entries are keyed in for a 2nd mail, sent, submitted, and all entries get cleared with no message of being sent/redirected. The mail was not sent successfully. Page reloaded, same problem.
I thought it was W3TC, disabled, still has the same problem.
P.S. Jetpack is disabled