The conditional in the buildAttribute function of buildMISPAttribute.py checking to see if the current object being processed is a URI, Link URI, or Link object leads to the subsequent conditionals never being processed, as it will always return true.

The bug is on line 560:
elif type_ == uri_object.URI or type_ == link_object.URI or link_object.Link:

and should be changed to:
elif type_ == uri_object.URI or type_ == link_object.URI or type_ == link_object.Link: