We recommend Stryders to set up their Garmin watch to take pace and distance from Stryd over GPS as Stryd pace and distance are more accurate. If you run with your Garmin watch set up as such, and you might get peaks in your pace data in Garmin Connect and PowerCenter.
This happens is because Garmin momentarily loses ANT+ connection with Stryd. To reconcile the accumulated distance, Garmin assumes incorrectly that pace must have been very high.
You can try to improve the ANT+ connectivity by wearing Stryd on the left foot and Garmin on your right wrist.
If that does not help, you can reconfigure the watch to use pace from Stryd and distance from GPS. You will still have accurate pace information on the watch. Distance accuracy will vary with GPS reception.