We study experimentally the stability of excited, interacting states of bosons in a double-well optical lattice where the nonlinear interactions are expected to induce "swallowtail" looped band structure. By experimentally preparing different initial coherent states and observing their subsequent decay, we observe distinct decay rates in regimes where multi-valued looped band structure is expected. This qualitative agreement with a dynamic homogeneous Gross-Pitaevskii calculation is not, however, matched by a quantitative agreement for the stability of the excited loop states. I will discuss potential explanations for this discrepancy and further work on this phenomenon.