I’m having a similar issue. When I fold open a field the label inputfield is gone. With firebug/webdev I find the label is empty
<div class="acf-input-wrap"><input type="text" id="acf-field-field_53f3482a60aad_label" class="label" name="fields[field_53f3482a60aad][label]" value="Nieuw veld" placeholder=""></div> and bootstrap.min.css has .label:empty { display: none; }
After a lot of trail and error I found out another plugin caused this (in this case Responsive Admin Maintenance Pro With Countdown). So check other plugins (deactivate them and refresh your form page. Maybe this way you can find out if another plugin interferes.
