I2C does not work after save (Espruino Pico)

Consider the I2Ctest script below. After a 'send to Espruino' and running 'onInit()' everything works fine. After a 'save()', I2C fails.

My hardware is OK, I have 2 pullups on B6 and B7 and a single DS3231 on the bus. An oscilloscope does not show any activity on either SDA or SCL, so how can a timeout is detected...

function init()
{
  //I2C1.setup({ scl : B6, sda: B7 });
  try {
    I2C1.writeTo(0x68,0);
    var data=I2C1.readFrom(0x68,3);
    console.log(data);
	LED2.set();
  } catch (error) {
    console.log(error);
	LED1.set();
  }
}

function onInit()
{
  I2C1.setup({ scl : B6, sda: B7 });
  LED1.reset();
  LED2.reset();
  setTimeout(init,2000);
}
Gives output :

> |  __|___ ___ ___ _ _|_|___ ___
|  __|_ -| . |  _| | | |   | . |
|____|___|  _|_| |___|_|_|_|___|
         |_| espruino.com
 2v09 (c) 2021 G.Williams
>
>onInit()
=undefined
new Uint8Array([41, 85, 22])
>save()
=undefined
Compacting Flash...
Calculating Size...
Writing..
Compressed 81600 bytes to 3379
Running onInit()...
InternalError: InternalError: Timeout on I2C Write BUSY
> 

The behaviour is the same after power off/power on (with the console.logs removed). What am I doing wrong ?