Tried;
-getting an other type of RX868 controller from a working FS20 device
Same result, only when I hold the FS20 TK within 20 cm of the RX868 controller, I recieve a complete package.
I've did some other testing, I've connected a LED to digital port, and light it up, every time a interrupt occours.
Using this test setup, I do see a change in the LED when I press the FS20 TK, even over great distance.
So it must be a software thing. Something to so with timers/timing.