If your SENSE readings are correct, then you may have a loose or bad connection at the breaker panel. You will probably need an electrician to come inspect and see if all your terminations are tight.
Or maybe the SENSE monitor has a bad chip that reads your voltage on L2.
Something you might try, is to check your house external ground connection. You can read my blog below and see that I improved my power quality by cleaning the contacts and using a new grounding clamp. Turn off all your power before you attempt this. I cleaned my ground rod connection using a battery-powered drill with a wire brush attachment. This may or may not help you. Maybe other users will reply with their ideas.