I don't mean to be difficult but I don't know what you mean by a simple diagram - the connections are all there in the schematic I posted. I can't draw anything different.
It's a Arduino Pro-mini 3V3/8M with a Atmega328P
The voltage regulator shown in the schematic is the SPX3819. I have to admit that I haven't looked at the spec for this. It seems to have an enable pin, which maybe gives the possibility of resetting it via the arduino so as to effectively reboot the NRF. The datasheet is here.
Unfortunately the enable pin is tied permanently high according to the schematic so I would have to cut a trace to change that.
The LIPO is currently around 3.8 V - of course fully charged it would be about 4.2V. But I don't now think the LIPO is the problem since the same thing has happened with the bench supply.