Database insert inserts twice

I have a database insert. But it inserts a new record twice. No errors or bug report.
Form code is:

<form id="frmfotosend" method="post" is="dmx-serverconnect-form" action="dmxConnect/api/pages/fotowedstrijd/album/insertalb.php" dmx-on:success="notifies1.success('Uw inzending is succesvol geupload en verzonden');frmfotosend.reset()">

Action step:

1dbaseinsert1320×734 152 KB

PhpMyAdmin print:

2myadmin1064×191 50.7 KB

Anyone who can tell me how this happens and, even more important, how I can fix this?