premature end of script headers: index.php on submit

Hello there, today I found out that one of my form that always worked perfectly, suddenly displays a 500 error and I found this in the error log:

Premature end of script header: index.php

I've checked pretty much everything, the redirect page works, emails are sent and data are stored correctly in the database so It seems more an issue with the redirect, but if I load the page (using the direct url) it all works.
Any idea what might be causing this error? Please note that there are 7 forms in this website and this is the only one that stopped working ;(
Thanks!

Hi elisa,

Does the form work from the View Form link in the Forms Manager?

Does it work if you add &tmpl=component to the end of the URL and re-load the page?

Bob

Hi Bob, actually I cannot explain what happened but now everything is working fine, could it be a server overload, or something that depended on the VPS? I may look further into this with my provider
thanks!