Conditions that cause loose guitar braces can be attributed to exposure to too much heat, a dried out guitar or glue joints and vibration over time. Some of these conditions can be repaired from outside of the guitar, others cannot. Its worth having a look before replacing the guitar...
Viewing the inside of an acoustic guitar is made easy with the use of a laptop and a USB endoscope...
Finding loose glue joints and positioning rare earth magnets for regluing entire braces in certain areas is a snap
Using one magnet on the inside, and one on the outside to hold it in place makes a physical reference point for brace regluing...
Once the brace is installed and before the protien glue sets, you can check your work and make sure the brace is properly located before and after installing the gluing jacks...