[SalesForce] Using lightning:overlayLibrary does not reopen modal

I'm using the lightning:overlayLibrary to display a modal in a Lightning Component that's used in a Salesforce Community.

This works for the first time. The modal displays with the correct body and footer when the method handleShowModal() function is called, and closes correctly when clicking on the close button in the top right or when calling the notifyClose() function from a button in the footer.

However, when calling the handleShowModal() function for the second time (see below for code), it does not open again.
The example given is using $A.createComponents to create the body and footer at the same time, and this simply goes into auraproddebug.js when inspected in the developer tools, without any usable error messages.
I also tried it with just a body, using $A.createComponent, which gave an error message stating Unknown component 'markup://c:modalScheduleDemo'.

What could be the problem here? Would it be that I'm trying to create the c:modalScheduleDemo for a second time? Should I destroy it after closing the modal? Or should I simply reopen the model instead of creating the body and footer for a second time?

handleShowModal: function(component, start, end, resource) {
    var modalBody;
    var modalFooter;
    $A.createComponents(
        [
            ["c:modalScheduleDemo",
                {
                    start : start.format('YYYY-MM-DD HH:mm:ss'),
                    end: end.format('YYYY-MM-DD HH:mm:ss'),
                    resource: resource,
                    'aura:id' : 'modalBody'
                }],
            ['c:modalGenericFooter', {
                'aura:id' : 'modalFooter'
            }]
        ],
        function(contents, status, errorMessage) {
            if (status === "SUCCESS") {
                modalBody = contents[0];
                modalFooter = contents[1];
                component.find('overlayLib').showCustomModal({
                    header: "header title",
                    body: modalBody,
                    footer: modalFooter,
                    showCloseButton: true,
                    closeCallback: function() {
                        // component.find('modalBody').destroy(); <- doesn't work
                        // component.find('modalFooter').destroy();
                    }
                });
            } else {
                console.log(errorMessage);
            }

        }
    );
}

Edit:
I found that I need to expand my question.
The way I'm calling this handleShowModal() function is from an event callback from the fullcalendar library. When a timeslot on the calendar is selected, it fires this call back, which calls the function and the modal opens successfully. This works once, as stated above.

I've created a test button that also calls handleShowModal(). This works perfectly fine multiple times, opening and closing the modal.
Also when first opening the modal with the event callback, and closing it, the button still works, but the event no longer.