Tubular Tire - Stretched or torn?

First time mounting a Dugast tubular and heard a tear with one of the tires… Slight tearing sound… I have never heard this with a mass produced tubular.

Any idea if this was the tape ripping or normal stretch?? Also what is the best way to determine damage to a tire? I realize a bulge could indicate damage, but I often see bulging around the valve area.

Any knowledge is appreciated.