I have to try a bit but I very much can, somewhat consistently, get an upward input out of the right button.
Holy shit, man. This might just be the worst D-pad ever. Wow. Fucking, wow.
Have you ever owned a small squishy dpad device? GBA, DS Lite, Wii or Gamecube? Sounds like you're not used to it. Understandable, we haven't had one in years, especially more problematic small ones.
Just use it a lots, you'll find it becoming more responsive in passing days.