On Android, there is a known bug in RetroArch where two buttons won't register as being pressed together.

To correct that, change the Input Block Timeout from the default of 0 to 1, up to 4 if needed.

Think I usually set mine at 2.

Screenshot_20250222-200759.png

Probably doesn't help you any, but it's the only thing that came to mind on this.

Glad you got it resolved even if you don't know what happened. :)