Girls, what does this mean?

Girls, what does this mean? Has anyone had this experience? We're on gavage. When the little one eats, she moves like a caterpillar, her breast releases milk then takes again. I transfer to another breast and she eats calmly for the first 2-3 and then acts the same way... there is enough milk, weight is gaining well. I transfer because earlier...I don't understand what's holding her back.