From the docs, emphasis mine:
Sets the value of the subject node field identified by fieldName to value. This will fail and stop script execution if the value is not of the appropriate type. Returns true if the field is successfully set, false otherwise.
Looks like a typo in the the
getLabelListContent component definition. I have no idea what a "uri" type is, is that a valid BrightScript data type? Change "uri" to "string".
<interface>
<field id = "uri" type = "string" />
<field id = "content" type = "node" />
</interface>