I have no experience with Flight deck. Since it reads speed it is getting its signal from the wheel (or crank), and since it reads cadence it is getting its info on the gear from the STi. I therefore think the problem is with the start switch. The distance is calculated by counting turns and multiplying - if the start switch doesnt work it wont know that it has to start counting. Ask about this on the mechanics forum, or the road forum where there are a lot more flight deck users.