I don't know exactly what my problem is...
For now, I've solved it by modifying a few lines of code in the “modal.js” file:
From line 175
layout() {
if ($(window).width() > this.modal_forms.task.px_size(this.options.width)) {
this.$modal_dialog.css(‘max-width’, this.options.width);
//
sup.sn if ($(window).width() <= 768) {
this.options.width = $(window).width();
this.options.width = this.options.width - this.options.width / 20;
this.$modal_dialog.css(‘max-width’, this.options.width);
}
// sup.en
this.$modal_dialog.css(‘margin-left’, ‘auto’);
this.$modal_dialog.css(‘margin-right’, ‘auto’);
}