Excess application of tape can prevent mating threads from fully engaging, reducing the shear point of the threads. Combining thread seal tape with a pipe dope compound can also overload threads. Also, internal overhangs of loose material may constrict a joint or slough off and form a foreign body that could jam a valve seat.
If too much tape is applied, it can prevent the threads from fully connecting, reducing the point at which they shear. Using thread seal tape in conjunction with pipe dope compound can also cause excessive loading on the threads. Furthermore, loose material within an internal overhang may compress a joint or dislodge and form a foreign object that could block a valve seat.