DIAGNOSIS That is the front suspension spring binding and then releasing. It's a known issue on early production units. The spring isn't properly seated or lubricated.
FIX You need to lubricate the suspension shaft. Lift the front wheel. Wipe the shiny metal suspension shaft clean. Apply a thin coat of silicone-based grease or white lithium grease to the shaft. Do not use WD-40. Compress the suspension several times to work the grease in. The noise should reduce or stop.
IF THAT DIDN'T WORK The spring may be physically misaligned. Contact Segway support. They have a service bulletin for this and may send a replacement front fork assembly or damping kit.
HEADS UP Do not disassemble the front suspension yourself. The spring is under high tension. Incorrect reassembly can cause failure while riding.