Hi,
I’m unable to heal most of the time (80%) using UP on the Dpad so i can’t beat 1st boss unless i do a perfect play (not skilled enough yet).
I’m playing on Steam Deck Oled
I got the same issue with an Xbox Elite 2 controller (bluetooth).
Please Help ! 
Very frustrating
I’ve been playing on the OLED and not had any issues with it so far, so not a definite issue with the deck at least
You’re a funny Guy 
Have you resolved this issue yet? It happens to me too. At present I just back off as far as possible and spam the button until it works. This is obviously not ideal.