Hi,
I've noticed my pantry shelf pulling lsightly apart, it doesn't have major weight on it, actually we specifically made it lighter things, however if I move it I do notice there is some give. I'm worried over time it might fall. The image shows the two screws in the back, I tried tightening them but it didn't do much. Should I put another screw in the middle or a nail in between? What is best to do here or just leave it?

