Hi Fritz,
The first argument to xxf:evaluate-bind-property() must be the bind id, while in your call you're passing a set of nodes. You can set the value of all the fields in the `fields` section to their initial value with the following:
<xf:action ev:event="DOMActivate" ev:observer="reset-control">
<xf:action iterate="instance('fr-form-instance')/fields/*">
<xf:setvalue ref="."
value="xxf:evaluate-bind-property(concat(local-name(), '-bind'), 'xxf:default')"/>
</xf:action>
</xf:action>
http://wiki.orbeon.com/forms/doc/developer-guide/xforms-xpath-functions#TOC-xxf:evaluate-bind-property-And here is the source of the full form you can paste in Form Builder if you want to try this out.
https://gist.github.com/avernet/14b1729bed096da4516fAlex
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