We saw a issue with the configuration for a action availablity. If you configure it in JCR you discribe a Collection of Hashmaps because in jcr you have always the combination of propertyname and value. But if you export your app configuration into YAML you get also a Collection of Hashmaps. But with YAML the Java only understands a Collection of Strings.
So the Configuration of YAML and JCR is a bit different. It should look like this

nodeTypes:
  - 'mgnl:folder'

instead of this:

nodeTypes:
  - folder: 'mgnl:folder'

Please describe this in the documentation and maybe fix this issue in the YAML Export Action.