WASHINGTON — Grayson Rodriguez’s biggest problem in his first year with the Angels isn’t difficult to diagnose, even if there’s an obvious built-in explanation. “Consistency’s been the biggest issue,” the right-hander said Sunday after the Angels’ 6-5 loss to the Washington Nationals. “That’s been the hardest thing to figure out.” Still, Sunday’s start offered some encouragement for Rodriguez’s trajectory, especially after giving up five runs in four innings on Monday at Boston.