Hi Martin,
thank you for your fast reply 
I am using the NewRemoteSwitch Library for 433Mhz signals. I have used that library with the Arduino Uno and YUN and it works great. I do not know exactly the signal width and frequency. The only thing I know is that the attachInterrupt function for external interrupts works with the Uno and YUN like a charm. Both of them are based on 16MHz oscillator. I tried to slow down the interrupt function of the MKR1010 with a fixed timer5 library and called the attachInterrupt function inside the timed based interrupt function. It worked but not reliable enough. It seems that this was the evidence that a frequency change could solve the problem. What do you think about that?
Thank you very much for your help!
Best regards
Alex