Tables in Textboxes

I have textbox that has three tables inside of it. Two of the three tables fit inside the textbox perfectly, but the other one overflows the textbox when I am looking at the preview. They all have the same table settings. The only difference with the one that doesn’t work is that it has 7 columns and the other two have 5. Does anyone have any thoughts on how to fix this? (I’ve tried changing from 100% to 75% and 50% in the table properties, but it just doesn’t help.)