Do you use a case on your note 20? Only reason I'm asking incase your case is one with magnets. Which can effect the s pen. If so do the test without the case on.
Good idea as case does have magnet but not where dead zone is and didn't used to be a problem! Thought occurred, magnetic charging leads and leaving plug in!
Not to do with charging! It is leaving the magnetic plug in the phone which was done to avoid continually plugging in and out and wearing socket on phone!