Thanks for sharing the training peaks link.
Was this an indoor test on a treadmill? How long was your warm-up before you started tracking heart rate?
Your heart rate stabilizes around 148-150 after 10 minutes. Was this your target heart rate?
Based on the averages you shared heart rate drift is 5.9%. If you warm up was only 10 minutes, I would redo this test with a longer warm up and let the heart rate stabilize around target heart rate (150) before starting the test.