This occurred in Igloo 5.0.0 and 5.0.1, where the button data type was faulty in the package import file from Umbraco. This will cause issues on some widgets where they won't render because of the data not being correct. Unfortunately this will not update automatically on update since we can't overwrite the existing document types without compromising what already has been built in Igloo.
However this can be fixed by manually changing the data type. Often the data type will have a similar name to the property on the document type. An example can bee seen below on "Level of Children" on The Navigation widget.