Form label covers form option

Expected behavior The form code is shown in the next snippet, and showing the behaviour as expected. Snippet in MDBootstrap

Actual behavior If I put the same code in the form on my site, than the first option shows up and covers the label. The following js-code is loaded just before the

  // Material Select Initialization
 $(document).ready(function() {
 $('.mdb-select').materialSelect();
 $('.select-wrapper.md-form.md-outline input.select-dropdown').bind('focus blur', function () {
 $(this).closest('.select-outline').find('label').toggleClass('active');
 $(this).closest('.select-outline').find('.caret').toggleClass('active');
 });
 });

Resources (screenshots, code snippets etc.)

<div class="md-form"><input type="text" id="myname" class="form-control" name="name" value="" required=""><label for="myname">Uw naam:</label></div><div class="md-form"><input id="myemail" class="form-control" type="email" name="email" value="" required=""><label for="myemail">Uw e-mail adres:</label></div><div class="md-form"><div class="select-wrapper mdb-select md-form colorful-select dropdown-ids"><span class="caret">▼</span><input type="text" class="select-dropdown" readonly="true" data-activates="select-options-4c6ffbb8-dd22-423c-a5cc-1ca83e9a4d6b" value=""><ul id="select-options-4c6ffbb8-dd22-423c-a5cc-1ca83e9a4d6b" class="dropdown-content select-dropdown w-100" style="width: 825px; position: absolute; top: 0px; left: 0px; opacity: 1; display: none;"><li class="disabled active"><span class="filtrable">Kies een optie</span></li><li class=" "><span class="filtrable">Via een forum</span></li><li class=" "><span class="filtrable">Zoeken op internet</span></li><li class=" "><span class="filtrable">Via socialmedia</span></li><li class=" "><span class="filtrable">Ben eerder op deze site geweest</span></li></ul><select id="inquiry_type" class="mdb-select md-form colorful-select dropdown-ids initialized" name="inquiry_type"><option value="" data-cgbf-human="Keuze" disabled="" selected="">Kies een optie</option><option value="forum" data-cgbf-human="Via een forum">Via een forum</option><option value="search" data-cbgf-human="Search Engine">Zoeken op internet</option><option value="socialmedia" data-cbgf-human="Via socialmedia">Via socialmedia</option><option value="customer" data-cgbf-human="Customer">Ben eerder op deze site geweest</option></select></div><label class="mdb-main-label" for="inquiry_type">Hoe heeft u deze site gevonden?</label></div><div class="md-form"><textarea rows="3" id="comments" class="md-textarea form-control" name="comments" data-cgbf-required=""></textarea><label for="comments">Uw bericht of vraag:</label></div><div class="form-group col-4 pl-0"><button type="submit" class="btn blue-gradient btn-block btn-sm btn-rounded z-depth-1a waves-effect waves-light">Verstuur</button><button type="reset" class="btn blue-gradient btn-block btn-sm btn-rounded z-depth-1a waves-effect waves-light">Reset</button></div><input type="hidden" name="returnid" value="30"><input type="hidden" name="m53a12form" value="contactForm"><input type="hidden" name="mact" value="CGBetterForms%2Cm53a12%2Cdefault%2C0&amp;amp%3B__c=02646e984a8f5dc168a"><input type="hidden" name="__guid" value="BAB91560-1364-420F-BD76-2FB2A3AE8FCC"><input type="text" style="display: none;" name="__hpname" value="">

Any thoughts?