So, after pulling my (now grey) hair, end after trying different sketches, both stable and beta version (2.0.1) of mysensors, different boot loaders, different fuses and so on, I discovered that if I connect the radio via cables and not directly to the board everything works as expected. Tried different radios and different boards with the same result.
There are 2 caps near the radio, 10uF and 100nF.
I´m not that skilled in electronics, so how come? Anybody knows? Is the radio to close to the mcu?
Attached is a picture showing my boards.