CF4 displays form again on submit instead of submitting

I'm Using CF4 on multiple websites and experiencing some problems on different sites now.
When submitting the form, the form is displayed again (with no data filled in).
When erasing the Joomla cacha en expired cacha, sometimes a form is send (and debugger info is shown). Cannot find any pattern in sending, not sending..

This happens on websites with Joomla 3.4.5 and component v4.0.6 and plug v4.0.3.

Hi JBS,

If the form is re-displayed instead of submitting that sounds like a problem with SEF URLs. Please see this FAQ

I can think of no reason why the form would submit when you clear the cache - or why that would display debugger data.

Bob

Hi Bob,

Thanks, this seems to be the trick. I have set 'Relative URL' setting to 'No' on a form, and sending is working again.
(All my forms are forms in a content item by the way).

I'm experiencing this problem om multiple websites. Do you have any idea what caused this problem ? Upgrade to Joomla 3.4.5? Untill now I have never had this problem before.

JBS

Hi JBS,

I suspect that something has changed in Joomla! 3 - maybe 3.3. - with the way that the Joomla! SEF works. I have seen many more reports of this problem than we ever did with earlier versions.

Bob

Hi Bob,

Checking some more websites and on some the forms works fine like before, some others have the problem as described.
If someone has any idea what caused this problem (new Joomla version, combination with any other extension, server setting, ...?), I'm very interested.