When I'm using a Pencil in Lightroom I'm not intentionally giving any finger touch inputs whatsoever. Photoshop on the iPad has a "Stylus only painting" option that ignores finger touches on the canvas and only accepts touches from the stylus. Lightroom for iPad needs the same setting. There's a brush tool in Masks that I use all the time, and this is no different from painting in Photoshop. Unfortunately not having this setting means that errant touches happen all the time. I'm especially having this issue right now. See the attached photo. See all those straight lines? Those are happening because Lightroom is connecting a touch (my hand resting on the screen while I use the Pencil) with the pencil itself when it hits the screen.