Garmin Training Center shows a different distance as TrailRunner does

Problem: Your ForeRunner device displays a distance for a workout. Garmin Training Center displays the same distance but TrailRunner displays a different distance.
Background: During the workout, your ForeRunner records geographical data points. At the same time your ForeRunner internally adds up the distances as a total distance so far. If you have intelligent recording enabled on your ForeRunner and the GPS signal quality isn't too good, the device will alter the recorded geographical course -- and therefore the derived distance -- after it knows better. Problem is that at the same time the overall distance should also be adjusted, which is not the case.
Status: To avoid confusion, TrailRunner usually displays the distance your device is displaying. But it could happen that the real distance, based on the mere data points, "slips through" in TrailRunner. This indeed is contradictory information but at the same time it is like impossible to me to "do it right".