There are many factors that can cause faults in bread, both external and internal. Some external faults include improper volume from too little or too much yeast, under or over fermentation, or too high oven temperature. Internal faults include holes and tunnels from weak flour or improper mixing, as well as cores from uneven mixing or skin formation during proving. Addressing factors like dough consistency, fermentation time, and oven conditions can help reduce faults.