  Ultracold molecules undergo "sticky collisions" that result in loss even for
chemically nonreactive molecules. Sticking times can be enhanced by orders of
magnitude by interactions that lead to non-conservation of nuclear spin or
total angular momentum. We present a quantitative theory of the required
strength of such symmetry-breaking interactions based on classical simulation
of collision complexes. We find static electric fields as small as $10$~V/cm
can lead to non-conservation of angular momentum, while we find nuclear spin is
conserved during collisions. We also compute loss of collision complexes due to
spontaneous emission and absorption of black-body radiation, which are found to
be slow.
