Running Civi 4.7.27 / Drupal 7.59
I have developped a rather complex Webform to enable the registration of several participants, with conditionals and associated Contributions, to an Event (I already have had several of this kind without any problem).
But with this one, when I complete the registration, I get an "Unexpected Error".
Then, if I come back to the form (via the browser back arrow), and re-register, everything runs OK.
Of course, I Can't put this webform in production without solving this : any help is welcome.