Getting very random results using OneWire on MDBT42Q

I'm getting very random results using DS18B20 one wire probes on two MDBT42Q boards. I'm using the latest firmware (as of March 2) but even simple searches for probes turns up unreliable results.
I'm using pin D11, have two DS18B20 probes that I've used reliably with other hardware (not Espruino), the probes' VDD pin is hard wired to VDD and I have a 4.7K pullup resistor.

Here is the code:

var ds = new OneWire(D11);
var sensors;
digitalWrite(D3,0);
function searchFor() {
  digitalWrite(D3,1);     // pulse trigger
  ds.reset();
  digitalWrite(D3,0);     // pulse trigger
  sensors = ds.search();

if (sensors.length >= 1) {
  console.log("Found "+sensors.length+" probes!");
  console.log(sensors);
  
} else
  console.log("No One Wire probes found!");
} 

setInterval(searchFor, 20000);   // search every 20 seconds

Attached is a snap of the IDE output.

1 Attachment