I’m not a doctor. But, it looks like you just put on the device, you forgot to wet the pads, and you were moving too much while the strap wasn’t tight enough. At the 16 second mark everything looks normal. But I’d check to see if that J segment is normal for you.

My guess is the sensor was moved while you were wearing it. Try running an real-time “ECG” on your smartphone and then move the device and your body around and see how the graph reacts.