Some checks showed, that obviously the events are read correct, if I see this corect. Please see:
$ acpi_listen
button/mute MUTE 00000080 00000000 K
button/volumedown VOLDN 00000080 00000000 K
button/volumeup VOLUP 00000080 00000000 K
9DBB5994-A997- 000000d0 00000000
button/f20 F20 00000080 00000000 K
9DBB5994-A997- 000000d0 00000000
video/brightnessdown BRTDN 00000087 00000000
9DBB5994-A997- 000000d0 00000000
9DBB5994-A997- 000000d0 00000000
video/brightnessup BRTUP 00000086 00000000
Looks like they are not interpreted somehow.....
Hans