The collection page linked shows scripts that are not present on the index template. Be sure that the theme is including those scripts on the home page. This does not mean there's not a conflict, but get this error out of the way first.
It's quite likely you've got a condition in theme.liquid like:
{% if template contains 'collection' %}
<script src="your-script"></script>
{% endif %}
You should extend that to also include the home page:
{% if template contains 'collection' or template == 'index' %}
<script src="your-script"></script>
{% endif %}