Ijust purchased a Galaxy Note 4 and don't have any problems with the s-pen except when I try to play Tetris. It will not respond at all to the s-pen. Tetris is the only game I play and would really like it to work.
I would contact the Developers and request S-Pen support. Keep in mind Note users are a small percentage of their market. Still something they should consider.
Good Luck!
Ron