I'm on 6.5.2 - Using the SPA Editor for Angular.  Coral 3 for authoring dialog.

I created create a simple Angular component and mapped it an AEM Component.  My AEM Component has an authoring dialog that has two multifields:

1) Multifield One : (Partial Snippet of Dialog)

<link sling:resourceType="granite/ui/components/coral/foundation/form/multifield" fieldDescription="Click '+' to add a new link" fieldLabel="Links" jcr:primaryType="nt:unstructured" composite="{Boolean}true">
<field sling:resourceType="granite/ui/components/coral/foundation/container" jcr:primaryType="nt:unstructured" name="./links">
<items jcr:primaryType="nt:unstructured">
<linkText jcr:primaryType="nt:unstructured" sling:resourceType="granite/ui/components/foundation/form/textfield" fieldLabel="CTA Text" required="true" name="./linkText" />
<linkPath jcr:primaryType="nt:unstructured" sling:resourceType="granite/ui/components/foundation/form/pathbrowser" fieldLabel="CTA Link Path" required="true" name="./linkPath" />
<linkTarget jcr:primaryType="nt:unstructured" sling:resourceType="granite/ui/components/foundation/form/select" fieldLabel="CTA Link Target" name="./linkTarget">
<items jcr:primaryType="nt:unstructured">
<same jcr:primaryType="nt:unstructured" text="Same window" value="" />
<new jcr:primaryType="nt:unstructured" text="New window" value="_blank" />
</items>
</linkTarget>
</items>
</field>
</link>

2) Simplified Multifield

<headlines jcr:primaryType="nt:unstructured" sling:resourceType="granite/ui/components/foundation/form/multifield" fieldDescription="Click 'Add field' to add new content dropdown." fieldLabel="Headlines">
            <field jcr:primaryType="nt:unstructured" sling:resourceType="granite/ui/components/foundation/form/textfield" required="true" name="./headlines" />
</headlines>

In the SPA editor, I can update the authoring dialog fields for both multifields and can see the changes reflected in the JCR through CRX. What I do not see is updates to  Multifield One in the model.json. But I can see updates to Simplified Multifield updating in the model.json.

I'm curious... Why do complex multifields get ignored by the Model.json (provided by JS SDK)? 

Providing sample files:  Sample Component Files 

1. en.model.json - Highlighted section with missing child nodes

2. zip file with content and dialog