In some cases, flexible metal conduit couplings may experience wear and tear due to mechanical stress. Over time, the coupling can become damaged from repeated movement, vibration, or expansion and contraction of the conduit material. This type of failure can lead to cracks or breaks in the coupling, potentially causing a loss of protection for the electrical wiring. To prevent this issue, it is important to select a flexible metal conduit coupling that is specifically designed to handle the stresses of the installation environment. Using appropriate strain relief methods and avoiding over-tightening or under-tightening the coupling can help minimize the risk of mechanical damage.