I bought a 90mm compression plug so it would extend about 30mm into the bike's head-tube. But when the carbon steerer tube was cut to desired length, the compression plug could only be inserted to 75mm depth. When I looked inside the tube, there was some immovable debris down inside it, apparently from the manufacturing process. I can't clearly make out what it is. Is that a normal thing with carbon forks? The obstruction begins about 9cm above the fork's crown.