Pace

Can anyone make sense of the pace graph below? Its tracing fairly accurately up to 4:30 minutes at just over 6:10 per m/km, then for no apparent reason states that I am running at 1.51m/km (I wish) its done that until the end of the run, however the pace average for the entire run is about right at 5:59m/km. This has never happened before to me. ciq.forums.garmin.com/.../1327545.png