Chronoforms v5 on Joomla multipage form sends empty emails

I created a multipage form on one of my websites, with all kind of required fields. I also added server validation to the form. As an example i added one of the emails that is send at the bottom:
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As you can see, some of the fields are filled, and some not. Also the form has to upload some images to the email. Those images are correctly attached to the message. All the fields mentioned in the email are required on the form.
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When the user tries it again, all fields are properly filled, same browser, same notebook. Am i missing something in the settings of the server validation or do i have to add another kind of validation.
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Tanks in advance for helping me.
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Aanmelding :
Persoonsgegevens:
Naam
Voorletter(s)
Roepnaam
Geslacht
Geboortedatum
Naam en voornaam volgens paspoort
Contactgegevens:
Adres
Postcode en woonplaats
Telefoonnummer
Email
Reisgegevens:
Naam kamergenoot (indien van toepassing)
Reis
Kamersoort
Begeleider
Kamersoort
Begeleider
Kamersoort
Begeleider
Kamersoort
Begeleider
Verzekeringsgegevens
Zorgverzekeraar
Soort aanvullende verzekering
Reisverzekering
Maatschappij
Internationale alarmnummer
Calamiteiten:
Naam
Telefoonnummer:
Adres
Postcode en woonplaats
Relatie tot betrokkene
Akkoord
Plaats akkoord: Alkmaar
Datum: 24-12-2018
Medische en overige informatie is te vinden in de database

Hi Hilco,
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Sorry but I don't understand your question - I think that something got lost in translation :-(
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Bob

Hi Bob,
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The problem is that a sometimes forms are emailed empty. If you want to see an example of the form, see this link
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Most of the times the email is properly filled with all the required information we need. But sometimes the email is empty.
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I hope this makes things more clear for you ;-)
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Hilco

Hi Hilco,
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Then there are two main possibilities:
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+ your serverside validation is not set up correctly. It needs to be before the Email action and have an Event loop or Showstopper action in the pink On Fail event.
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+ the emails are being sent by a webbot browsing the URLs on your site - however, the serverside validation should still prevent this.
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Bob

Hi Bob,
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At first a happy new year. I am responding a little bit late, because of my holiday.
About your answer, emails are nog sent by a webbot. I am sure of that because we had some phone calls from users when the forms were send empty. Those calls match the number of empty forms.
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For the setup of the serverside validation, i added screenshots of the setup. Maybe you can see what is wrong there?[file=11337]screen1.PNG[/file]
​[file=11338]screen2.PNG[/file]
​[file=11341]screen3.PNG[/file]
​[file=11342]screen4.PNG[/file]