  We show that higher form fields, specifically 2- and 3-forms in four
spacetime dimensions, suffer from loss of hyperbolicity when they have self
interaction. The equations of motion lose their wave-like characteristic in
certain parts of the configuration space, and such problematic regions can also
be reached dynamically from healthy initial data. These findings are analogous
to recent results for vector fields, which are equivalently 1-forms, however,
the details of the pathology can be different for higher forms. We also show
that the possibility of more than one self interaction term in higher forms
also leads to the amelioration of hyperbolicity problems.
