Nintendo joycons doesn’t work properly

[m3mento]

Hello, I tried to configure the two Joy-Cons in combined mode, as shown in the guide. The Joy-Cons work fine in the menu, but when I launch a game, the buttons respond erratically — they register maybe 1 out of every 10 presses.
However, if I connect just one Joy-Con in horizontal mode, everything works perfectly.

I have the impression that when connecting in combined mode, there’s interference, as if the system sees three controllers: left, right, and combined. In fact, under Controller Settings I can see 3 inputs: left Joy-Con, right Joy-Con, and the combined one.

I’m not sure if that’s the actual issue or something else.
Has anyone managed to use the combined mode properly?
Any help would be appreciated. Thanks in advance!
Raspberry pi4