We've got some reports of this but unfortunately can't reproduce it. According to some research we've done (*), it doesn't seem specific to GoodNotes and we suspect it could be related to the specific Apple Pencil or iPad. Many affected users no longer experienced this after having Apple replace the Pencil, and/or the iPad.
If you don't happen to have another Apple Pencil or device to try, immediately write in another note-taking app as soon as the issue pops up to see if it occurs there.
Here are some additional suggestions that worked for some of the users. See if any of them work for you too:
- Move your iPad away from another device (computer, Apple Watch, charger, etc.) to remove possible static interference.
- Tap the metal part of your iPad when this is happening to remove possible static interference.
- Unscrew the Pencil tip and clean the contact part where the tip is screwed on.
- Make sure your Apple Pencil is indeed working correctly.
- Don't use the iPad while it's charging, and if you have to, use an Apple charger, not a third-party one.
- Lower the sensitivity of the double-tap gesture of the Apple Pencil 2, or turn it off altogether.
- Keep your palm and the glass surface dry (i.e. no sweaty palm)
- Change the screen protector.
- Use the Fountain Pen instead.
- Set Palm Rejection in GoodNotes to High.
- Restore your iPad. But back up all your GoodNotes data first.
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(*) References:
https://www.reddit.com/r/GoodNotes/comments/iawnsz/ipad_pro_2020_apple_pencil_2nd_gen_random_lines/
https://discussions.apple.com/thread/7622195
https://discussions.apple.com/thread/7913829
https://forums.macrumors.com/threads/ever-seen-this-weird-apple-pencil-glitch.2019539/
https://www.reddit.com/r/ipad/comments/hyssbv/ipad_pro_with_apple_pencil_behaving_weird_what/
https://www.reddit.com/r/iPadPro/comments/jfrcm8/ipad_writing_issues/