Do you really need the plane stress assumption or can you use a single layer of solids instead? Solids make everything more robust.
Force loading with contact often fails when the part with the force isn’t supported except by the contact. Contact alone doesn’t seem to be enough to reliably solve the first increment, perhaps it’s initially open so there’s rigid body motion? A guiding principle is to treat the free part like a woman - gradual application of forces and gently constrained against flying away. If you just throw it at the wall, it might break.