Full Calendar Initialisation size issues

I have a multi step type form
It starts off with a radio button page, depending on what the user clicks it then shows my event calendar

<dmx-value id="var_which_page" dmx-bind:value="0"></dmx-value>

<div class="row mb-5" dmx-show="var_which_page.value == 0">
    <div class="col-12 p-5 text-center rounded">
        <h3 class="text-white mb-5">Do you want to book now?</h3>
        <div class="row">
            <div class="col-6">
                <div class="bg-white rounded py-3">
                    <input class="form-check-input m-0 p-0 border-3" type="radio" value="Book" id="radioBook" name="radioBook" dmx-on:click="var_which_page.setValue(2);radioDone.select(false)">
                    <label class="form-control m-0 border-0" for="radioBook">Book Now</label>
                </div>
            </div>
            <div class="col-6">
                <div class="bg-white rounded py-3">
                    <input class="form-check-input m-0 p-0 border-3" type="radio" value="Done" id="radioDone" name="radioDone" dmx-on:click="var_which_page.setValue(1);radioBook.select(false)">
                    <label class="form-control m-0 border-0" for="radioDone">Book Later</label>
                </div>
            </div>
        </div>
    </div>
</div>

<div class="row mb-5" dmx-show="var_which_page.value == 2">
    <div class="col-12 p-5 text-end rounded">
        <dmx-value id="varEventClicked"></dmx-value>
        <dmx-calendar id="phCal" timezone="UTC" view="timeGridWeek" hide-non-current-dates="true" no-fixed-week-count="true" dmx-on:eventclick="sc_how_many_already_booked.load({event_start_selected: $event.event.start});" event-order="start,-duration,title">
            <dmx-calendar-source id="calSrc" dmx-bind:events="sc_calendar_events.data.query_events" event-start="adt_StartDateTime" event-end="adt_EndDateTime" event-title="" event-id="adt_id" color="#000"></dmx-calendar-source>
        </dmx-calendar>
    </div>
</div>

When the user clicks book now and the calendar shows the size is wrong like it has not initialised.
If i make the calendar shown all the time then its perfect, it just does not seem to like showing a calendar that was previously hidden.

Anyone got any ideas.