We believe there is an issue with users' wifi connections interfering with their GPS signal when they run past wifi hotspots. To test this, please try turning off your phone's wifi for your next run, to see if that improves the accuracy of your GPS tracking.
Unfortunately, there can also be occasional GPS anomalies which cause this kind of erroneous run record. Unless this kind of problem recurs frequently, it's unlikely to be a problem with the app itself. Should this become a recurring problem, please do let us know and we'll investigate further.