SMA sunny webbox data with script

I’m brand new to OPENHAB and so far quit happy with it. I got my FritzBox and all the Thermostats and powerplugs running on OPENHAB and some other stuff. So far so good. Now I tried to got the information of my solar powerplant which is connected to an SMA sunny Webbox. There is a procedure with an RPC request that shold be answered by the webbox and provide the values. To do this I created a script:

curl -X POST –silent -d ‘RPC={“version”:”1.0″,”proc”:”GetPlantOverview”,”id”:”1″,”format”:”JSON”}’ -H ‘content-type:text/plain;’

and an thing

Thing exec:command:GetPlantOverview [command="sudo -u openhab /etc/openhab2/scripts/",interval=120000,timeout=10000,autorun=false]

and the items that belong to it:

//SMA Wechselrichter Abfrage über RPC

Number GriEgyTot    "Gesamtertrag"  (gSolar) {exec="<[/etc/openhab2/scripts/$.result.overview[?(@.meta=='GriEgyTot')][0].value)]"}
Number GriEgyTdy    "Tagesertrag"   (gSolar) {exec="<[/etc/openhab2/scripts/$.result.overview[?(@.meta=='GriEgyTdy')][0].value)]"}
Number GriPwr       "Leistung"      (gSolar) {exec="<[/etc/openhab2/scripts/$.result.overview[?(@.meta=='GriPwr')][0].value)]"}

//Number GriEgyTot    “Gesamtertrag”      {exec=”</etc/openhab2/scripts/$.result.overview[?(@.meta==’GriEgyTot’)][0].value)”}
//Number GriEgyTdy    “Tagesertrag”       {exec=”<[/etc/openhab2/scripts/$.result.overview[?(@.meta==’GriEgyTdy’)][0].value)]”}
//Number GriPwr       “Momentanleistung”  {exec=”<[/etc/openhab2/scripts/$.result.overview[?(@.meta==’GriPwr’)][0].value)]”}
String GetPlantOverview_out     "Ausgabe SMA-WR"        (gSolar) {channel="exec:command:GetPlantOverview:output"}
String GetPlantOverview_exit    "Status"                (gSolar) {channel="exec:command:GetPlantOverview:exit"}
String GetPlantOverview_lastex  "letzte Ausführung"     (gSolar) {channel="exec:command:GetPlantOverview:lastexecution"}

The problem now is, that the script seems to run because in the log I found the entry:

2019-02-14 17:53:40.870 [vent.ItemStateChangedEvent] - GetPlantOverview_lastex changed from 2019-02-13T08:33:40.747+0100 to 2019-02-14T17:53:40.808+0100

But on the sitemap all items are empty. If I look in the PaperUI i can see the last exec timestamp and an error message grafik
Can anybody help me solving this problem?