Our son's crib has a solid back and I hate it. My brother in law gave it to us, their son never slept in it. We have mesh bumpers on the other 3 sides but can't put anything along the solid back. He favors that side of the crib, always rolling onto his tummy right up against the back. My worry is that he constantly slams his knees and head into the back of the crib when he rolls around. It sounds horrible and I'm scared he's doing damage to his head. 😢 This happens 2-4 times almost every night. He's 7 months old. What can I do?