Domoticz

My garden pond pump has a ACM1000 Switch, (433MHz) , simple system ( it doesn't send information back)
When I send by a hand-remote or Wall-switch remote, the acm goes on and Off.
In Domoticz i have learned this switch by pushing the hand-remote.
Now comes the problem: The On signal by Domoticz (through RFXCom) works, but the Off signal doesn't !

Another ACM 1000 for the garden light works great. It's identical to the pump one.

Ik have tried, to delete the switch in Domticz and Learned again, but that didn't solve the problem.

I had the perception that I worked with Z-wave. I had learned the device by a delivered small hand remote, but i switch my water pump by a hand wall mounted remote. Now I had to learn these remote's too, en program that timer for switching off by darkness, not the timer of the small hand remote.....