Pico power consumption down to 0.02mA

Have you tried just using a meter in current measuring mode rather than going across a resistor? I put a big (47uF) across it just to make sure any spikes are levelled out.

I did try just now with a Pico 1.4 (I'd been using a Pico 1.3 before) plugged into breadboard and the power consumption seemed a lot higher as you say (in the 0.5mA range).

However, after having put all the pins into input mode and then connected them to ground (not B6/B7 as these default to serial when USB is unplugged) I get back down to 30uA

digitalRead([B15,B14,B13,B10,B1,A7,A6,A5,A4,A3,A2,A1,A0,A10,B9,B8,A8,B7,B6,B5,B4,B3]);
setInterval(function() {
  digitalWrite(LED1, 1);
  setTimeout(function () {
    digitalWrite(LED1, 0);
  }, 20);
}, 10000);
setDeepSleep(1); 

Maybe someone else could give theirs a go?

I'm still really confused about why my 1v4 and 1v3 should be behaving differently though. The circuit itself is the same on the two revisions (just with the addition of a fuse, which isn't used for battery power).