I have been cooking kale for decades. Usually steamed, sometimes sauteed, occasionally massaged for a salad. Usually it's delicious and tender. But every once in a while, it just doesn't get tender. I cook it and cook it, but it takes way longer than usual, loses it's color, and is still kinda tough. This happens with both kinds of kale, curly and lacinato. And just looking at the kale, it doesn't seem to be any way to predict this. Has anyone else experienced this? Have you found a way to tell beforehand if a bunch is going to be a problem?