Recently I've bought a generic bluetooth keyboard from Carrefour. Nothing fancy, it seems that it was made with multiple platforms in mind. The model is CBK01 (OY661-1). This keyboard works great on Windows, it sends 2-3, maybe even 4 simultaneous key presses. But on Android it only sends one key at a time. I can't even write capital letters with it. The for now, the problem is partially solved via External Keyboard Helper, but only partially.
I've tried both Logitech's diNovo Mini keyboard and a wired keyboard (via OTG) and they both work just fine. So I guess the problem is somewhere in the middle. I just don't know where.
If anybody can help me solve this, even with a small hint, I'd be grateful.