Multiple nrf24l01, shared power, ripple/interference, DSO screenshot provided
Did you try LC filters out?

I am a little rusty on RFI &amp; EMI, but here is what I would try.

Background Logic:

Depending upon the frequency of the uC &amp; of course other crystal oscillators in the circuit, it could be possible that either power supply is giving up or the capacitors are unable to filter the ripples out.

The capacitors don't always have ideal frequency response as negative slope. In particular electrolytic capacitors may behave differently at different frequencies. At higher frequencies, they may even behave as inductors. Refer to Frequency dependence of electrolytic capacitors for similar discussion.

Experiment:

I think I would try a combinational solution: a set of electrolytic capacitors, ceramic &amp; polyester capacitors in parallel with each module in LC combinations. Each module has at least one inductor in series, two or three parallel capacitors of different kinds, that is.