I think I have found the solution. The settings in the fibaro may be the porblem. I have a flow to open and a flow to close the curtains. They work fine if I test them form the flow editor, but very weirdly when I press the fiber buttons. Check out this thread:
Basically paste in the following in the raw configuration and save it:
If you want to try out the raw configuration (to “resend” it), you can add 28,1,15;29,1,15
I’m so relieved that this problem I solved!