It's seriously annoying me too. Only just discovered that it's not actually me causing the terrible wobbly lines, but the Surface Pro 4! And this was the reason I bought the machine! Haven't they found a fix for this yet? I can't actually believe Microsoft okayed this product and actively pitched it as a production machine at creatives, and this glaring innacuracy with its performance was there all along!
I haven't been this frustrated with drawing in my life. Microsoft! Sort it out now! We didn't pay hundreds, or even thousands of pounds for our devices to be given this sub-standard performance!