Panasonic TV - failed with HTTP Reponse Code 400

Hello everybody,
after switching on my TV every morning (by rule via homematic switch) I’m looking for a solution to set TV-channel “1”.
I’m running openHAB2, using binding panasonictv v1.9 and device TX-L47DT50E

Following has been configured
file - panasonictv.cfg
tv_living=192.168.1.xxx

file - panasonictv.items
Switch WZ_TV_Digit_1 “Taste 1” { panasonictv=“tv_living:D1” }
Switch WZ_TV_Digit_2 “Taste 2” { panasonictv=“tv_living:D2” }

file - hifi.rules
rule "HIFI-TEST"
when
Time cron "0 15 18 ? * * *"
then
sendCommand(WZ_TV_Digit_1,ON)
Thread::sleep(500)
sendCommand(WZ_TV_Digit_1,OFF)
end

After using PAPERUI to install binding panasoinctv v1.9, I receive following log@openhab.log
2017-02-05 17:59:21.769 [INFO ] [asonictv.internal.PanasonicTVBinding] - TV registered ‘tv_living’ with IP '192.168.1.xxx’
2017-02-05 18:15:01.901 [WARN ] [asonictv.internal.PanasonicTVBinding] - Command D1 to TV with IP 192.168.1.xxx failed with HTTP Reponse Code 400
2017-02-05 18:15:02.403 [WARN ] [asonictv.internal.PanasonicTVBinding] - Command D1 to TV with IP 192.168.1.xxx failed with HTTP Reponse Code 400

Happy about any feedback, Markus