Meteor Autoform Custom Templates - templates

Question

This is a niche one - hopefully someone has had some experience with this before! Any pointers would be greatly appreciated.
Problem
I'm trying to use Autoform together with Autoform-Semantic-UI and nested custom templates. In the interface, the outer form loads, but when my custom templates load I get console errors referencing that the template cannot access any data, such as:
debug.js:41 Exception in template helper: TypeError: Cannot read property 'type' of undefined
at afArrayTracker.atInitField [as initField]
Exception in template helper: TypeError: Cannot read property 'slice' of null
at Object.autoFormGetLabelForField [as getLabelForField]
Exception in template helper: Error: Invalid field name: (not a string)
at Object.getDefs
This makes my form only partially rendered!
Code
client.js has the schema design:
Schemas = {};
Template.registerHelper("Schemas", Schemas);
Schemas.MarkingScheme = new SimpleSchema({
name: {
type: String,
optional: false
},
description: {
type: String,
optional: true
},
aspects: {
type: Array
},
'aspects.$': {
type: Object
},
'aspects.$.focus': {
type: String
},
'aspects.$.rubric': {
type: Array,
minCount: 1
},
'aspects.$.rubric.$': {
type: Object
},
'aspects.$.rubric.$.mark': {
type: Number
},
'aspects.$.rubric.$.criteria': {
type: String,
optional: true
},
comments: {
type: [String],
optional: true
}
});
Here's the template for the form, which works fine:
<template name="insertScheme">
<div class="ui large header">New Marking Scheme</div>
{{#autoForm schema=Schemas.MarkingScheme id="insertScheme" type="insert"}}
{{> afQuickField name="name"}}
{{> afQuickField name="description"}}
{{> afArrayField name="aspects" template="rubric"}}
{{> afQuickField name="comments"}}
<div class="row">
<div class="centered column">
<div class="two large ui buttons">
<button type="reset" class="ui button">Clear</button>
<div class="or"></div>
<button type="submit" class="positive ui button">Submit</button>
</div>
</div>
</div>
{{/autoForm}}
</template>
Now is where things go south, even though I've reverted to using a near carbon copy of the template used for the semantic-ui autoform package:
<template name="afArrayField_rubric">
<h4 class="ui top attached block header">
{{afFieldLabelText name=this.atts.name}}
</h4>
<div class="ui secondary bottom attached segment">
{{#if afFieldIsInvalid name=this.atts.name}}
<div class="ui pointing red basic label">
{{{afFieldMessage name=this.atts.name}}}
</div>
{{/if}}
{{#afEachArrayItem name=this.atts.name minCount=this.atts.minCount maxCount=this.atts.maxCount}}
<div class="field autoform-array-item">
{{#if afArrayFieldHasMoreThanMinimum name=../atts.name minCount=../atts.minCount maxCount=../atts.maxCount}}
<div class="ui mini red corner label autoform-remove-item">
<i class="icon minus"></i>
</div>
{{/if}}
{{> afArrayField name=this.name label=false options=afOptionsFromSchema template="aspects"}}
</div>
{{/afEachArrayItem}}
{{#if afArrayFieldHasLessThanMaximum name=this.atts.name minCount=this.atts.minCount maxCount=this.atts.maxCount}}
<div class="field">
<div class="ui small green icon button autoform-add-item" data-autoform-field="{{this.atts.name}}" data-autoform-minCount="{{this.atts.minCount}}" data-autoform-maxCount="{{this.atts.maxCount}}">
<i class="icon plus"></i>
</div>
</div>
{{/if}}
</div>
</template>
The idea is that it goes on deeper; but this is as far as we get.
Many thanks for any ideas of things to try!