Presumably you have these lines set:
input_shader_next_btn = “?”
input_shader_prev_btn = “?”
Check for them in your autoload files:
/opt/retropie/emulators/RetroArch/configs/
and your main retroarch file:
/opt/retropie/configs/all/retroarch.cfg
and your system specific files:
/opt/retropie/configs/{systemname}/retroarch.cfg
