Editing Song Select Lead Sheets

I am trying to add a harmony line to a lead sheet utilizing the pen app, but the app keeps moving my marks a bit. Is there a snap to grid function turned on in the app that I could disable? I checked my ipad and that function is not turned on in my general settings, but that’s my best case for what’s happening.

Also, is there an “white out” function I could use to make a slight change in the melody line?

Thank you,

Julie Ruch