Looks like you did not include ReadAuthRegistryTask.brs file, correct?
sub getFromLocalStorage(field, callback)
print("Get from local storage")
m.readAuthRegistryTask.control = "RUN"
What I would do is to add another string field to your task node for the "incoming" registry section, that your task will reference via m.top.FIELDNAME to know what registry section to query.
something like <field id="regSection" type="string"/>
then you pass it in, in the function I copied above, add the line before observefield line; m.readAuthRegistryTask.regSection = field
then your task can see that via m.top.regSection and once it reads the registry, the task should set its own m.top.authData field which should be the field that your observing in your calling function,
Hopefully you have a separate ReadAuthRegistryTask.brs file from what's shown here 🙂
hope this may help,