At times, I notice that my running pace appears to be inaccurate. Typically, I run at a pace of 6 - 7 min/km but there are instances when my watch displays a pace of 9 - 10 min/km. Additionally, I have noticed that my best pace at the end of a run is slower than my average lap pace. For instance, during today's run, my best pace was 6.12, while the average pace of my last kilometer was 6.05. Has anyone else experienced this issue?