Repeater for json field not working in data picker UI

Wappler: 5.1.5
OS: MacOS M1
Server: PHP/MariaDB

I have a json field in the database containing values to be shown as checkboxes in a form. This is the repeater code on the page:

<div dmx-show="questionType=='Checkboxes'">
    <div dmx-repeat:repeat1="questionOptions">
        <div class="form-check">
            <input class="form-check-input" type="checkbox" dmx-bind:value="$value" dmx-bind:id="'checkboxes_'+$index" dmx-bind:name="'checkboxes['+$index+']'">
            <label class="form-check-label" dmx-bind:for="'checkboxes_'+$index">{{$value}}</label>
        </div>
    </div>
</div>

The page works fine but the UI in Wappler just shows a spinner instead of the fields to use:

I’m putting the cursor in the code where {{$value}} is and clicking on the Client Side Data Binding thunderbolt button in order to get the variables but I only see the spinner.