Game controller registers all button presses when polled via /dev/input/js0, but not using /dev/input/event19

I have a Saitek Side Panel Control Deck which I've been trying to get to work under OpenSUSE Tumbleweed lately (kernel 6.15.2). I vaguely recall that I already had it working some time in 2021. The problem is that most games (all I've tested with) don't recognise all button presses. Even worse, KDE settings exhibits this problem too. Opening the game controller page of KDE settings correctly recognises the device, showing Mad Catz Saitek Side Panel Control Deck (/dev/input/event19) in the device selector and correctly listing all of its buttons. However, upon pressing some of them, they're eit

Question by Alexander Leithner on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.