Speed is intermittently not recorded/displayed, but distance and GPS track are correct.

Occasionally during an activity, my speed/pace intermittently is displayed as 0.0 but the distance I travel is still displayed correctly. While moving, my speed will suddenly display 0.0 but after a few minutes, the speed will correctly display again. After saving the activity, in Garmin Connect (app and website), the speed still shows 0.0 but the distance and GPS track are displayed correctly. 

Additionally, sometimes the start time of the activity is incorrectly recorded (the recorded start time will sometimes be almost an hour after the activity has ended). 

I am using the "Track Me" activity if that makes a difference.

Is there a way to troubleshoot this issue?

In the attached image, the speed drops to 0.0 even though I am moving at about 5 mph. The distance and GPS track correctly update even though the speed is recorded as 0.0