"Start + B" what does that combination do (and at what point do I have to press that combo for it to be effective)?

Just to clarify: Both contorollers (zero and SFC30) work in recalbox in bluetooth mode.
Just the "Press and hold R1" doesnt. If I press and hold L1 or R1 it registers as multiple presses.

Hi all

I'm currently playing Castlevania: Aria of Sorrow on GBA. Somehow I managed to finish nearly 50% of the game when I figured out I can't activate some of my abilities "Press and hold R1" doesn't work on my 8bitdo SFC30 controller.
Tried it with a old wired generic controler and "Press and hold R1" works, but not on 8bito Zero or SFC30.
Is there a fix for this behaviour or do I have to buy another controller?

Running: Recalbox 18.02, 8bitdo SFC30 firmware ver. 4.10

Thanks in advance