@Julia-J. the recommendations in https://www.dorkbotpdx.org/blog/paul/better_spi_bus_design_in_3_steps might be useful to make the bus more stable. You do have a capacitor for close to the nrf right? I know it shouldn't matter but unstable power often causes strange things to happen. Another alternative could be to use softspi to place the nrf on separate pins. An example is available at https://www.mysensors.org/build/ethernet_gateway As suggested in http://electronics.stackexchange.com/questions/166832/multiple-spi-busses-in-ribbon-cable?rq=1 connecting every second wire in the ribbon to ground can shield the signals from interference. Maybe lowering the SPI speed helps. I think that is done by setting //#define MY_RF24_SPI_MAX_SPEED 4000000 to something lower, maybe try 1000000 instead.