Lumpy jaw is usually the name given to an abscess of a tooth that causes swelling of the jaw.
The areas in the photo do not really look swollen but it is hard to tell in a photo.
I would take the glider to a glider experienced vet to have the areas looked at. They almost appear like a bite wound that has healed but not regrown fur. There may be some infection under the skin that would need antibiotic treatment. Only a vet can make that diagnosis and provide appropriate treatment.