NRF24L01+ how much supply ripple is acceptable?
I would suggest using a different power supply, that appears to be your problem.  250mV is 1/4 of a volt, that is a lot of noise/ripple.  I am assuming it is ripple from the AC mains.  The series resister is way to large, try something about 0.1 ohm.  Also put a filter cap on the load side of the resister.  If you have high frequency noise add a 0.01 cap that will help.  Be sure the grounds between the units are solid.

Gil

I have a feeling it is narrow fast rising spikes.  If so the odds are very high it is the power supply.  Can you try an analog one and see if the problem goes away?  Try adding more bulk capacitance, at the rate of at least 1000uF per amp.