KM forgets my usb device triggers (Apple Magic Keyboard)


I got an Apple Magic Keyboard connected to my Mac Pro via Bluetooth. I want to use a double-left-option-keypress as a trigger, so I used an "USB Device Key Trigger" which most of the times work (sometimes I have to tap the key multiple times to make KM recognize the key). When it worked there is a "Magic Keyboard with Numberic Keypad Left Option" key selected and everything works fine for some time. But after a while KM forgets the key assignment. I'm also not able to assign the key again. The only thing that helps ist stoping and starting the KM Engine.
Is this a known problem? Is this bluetooth related?