Your test case is failing when move_arm triggers a planning scene sync via the setPlanningSceneDiff service. Maybe inspecting the relevant source code will provide you with more clues. Here's the relevant source files involved, all belonging to the planning_environment package:
collision_models_interface.cpp contains the CollisionModelsInterface::syncPlanningSceneCallback(...), which is woken up on a sync request. Here's where "Setting planning scene state to NULL" comes from.
If you follow the method's logic, you'll pass through CollisionModels::setPlanningScene(...), in
collision_models.cpp, which is where "Incomplete robot state in setPlanningScene" comes from, and end up at setRobotStateAndComputeTransforms(...), in model_utils.cpp where the actual problem seems to lie. There's one code path towards the end that returns false, and does not log the failure reason. That's where I believe you should look into.