Thanks for looking, Lee. My PAW power source in the aircraft or at home is a Power Walker (10000, I think), solely feeding the PAW through its IPad output. I connect EasyVFR to PAW as per PAW Operating Instructions 20180129 pp13-16 with "Use FLARM GPS as EasyVFR GPS" set to OFF and vertical proximity 3000ft.
The system has been beautifully stable for the last year or more. I noticed that as long as I switched on PAW before EasyVFR, the PAW would connect without my having to do anything in Nexus Settings/WiFi. But over the last month or so it's been reluctant to connect in the first place without going into Nexus Settings/WiFi, and sometimes reluctant even then. I've tried forgetting PAW and reconnecting, which worked on one occasion when it was particularly reluctant, but it still dropped out later in the flight.
As I noted in my OP, I have PAW Network Settings Mode G rather than the Mode B called for in PAW Operating Instructions. I'm not conscious of having made a change, so presumably must have been told to do that at some stage. Is it relevant?