I2C, save(), onInit(), Internal Error - issues

Unfortunately that doesn't seem to work for me. On Espruino 1.58, the following code example works:

function onInit() {
  digitalWrite(LED3,0); //reset blue LED
  I2C1.setup({scl:B6, sda:B7});
}

onInit();

var nfc = require("PN532").connect(I2C1);
print(nfc.getVersion());
nfc.SAMConfig(); // start listening

setInterval(function() {
  nfc.findCards(function(card) {
    print("Found card "+card);
    card = JSON.stringify(card);
    if (card=="[4,238,254,40,117,69,0]") digitalWrite(LED3,1);
  });
}, 1000);

If I unwrap the onInit() function so the I2C1.setup() is run inline at the start, as soon as I type save() the Espruino reboots and I get the I2C errors. And every time it starts up after that.

It does seem to set it up though:

>dump()
var nfc = {
  "i2c":{
    "_options":{"scl":B6,"sda":B7}
  }
};
I2C1.setup({"scl":B6,"sda":B7});
digitalWrite(B6,0);
pinMode(B6,"opendrain");
digitalWrite(B7,0);
pinMode(B7,"opendrain");