Yes, ductwork that is leaking air occurs when it is installed improperly. This is an important issue to fix because it is costing you money by conditioning an area that doesn't need to be conditioned. And because duct is located above the ceiling, you're probably losing conditioned air. This is an issue a TAB service would find and report on. Duct leakage can significantly reduce performance and effectiveness of the HVAC system. It can negatively impact occupant comfort and increase energy use and cost. It is common and expected for general HVAC duct systems to have some amount of air leakage. Sealing for complete airtightness is cost prohibitive and unnecessary in most applications. Somewhere around 5 percent leakage could be considered acceptable for most general duct systems. Greater leakage, such as caused by improper connections and sealing, should be addressed prior to performing the air balance.