Without seeing your project it's difficult to know exactly what the problem is, however, I can guess at one or two things.
Default breakpoints are somewhat arbitrary. They are simple points across a scale of potentially hundreds of different resolutions. In most cases, a well-designed project will adjust for all the points between the breakpoints but it isn't truly foolproof. For example, you might have designed your smallest breakpoint for a certain resolution. That doesn't mean that you will be able to accommodate all the different screen sizes that might be below that resolution.
My advice would be to allow for more space than is necessary for your text captions or smart shapes. If you cannot fit all the text in that space lower the font size to accommodate these smaller screens.