onInit with HD44780

Beginner with espruino and having some trouble with onInit on my Pico:

function onInit() {
    I2C1.setup({scl:B6, sda:B7});
    var lcd = require("HD44780").connectI2C(I2C1);
    lcd.clear();
    lcd.print( "Hello World!" );
}

Upload and save() works as expected:

>reset();
=undefined
 _____                 _
|   __|___ ___ ___ _ _|_|___ ___
|   __|_ -| . |  _| | | |   | . |
|_____|___|  _|_| |___|_|_|_|___|
          |_| http://espruino.com
 1v88 Copyright 2016 G.Williams
>echo(0);
=undefined
>save()
=undefined
Erasing Flash.....
Writing.......
Compressed 81600 bytes to 4445
Checking...
Done!
Running onInit()...

But when I un- and re-plug USB it's not working - the LCD is staying blank:

Disconnected
Connected
>Loading 4445 bytes from flash...
Running onInit()...
=undefined
Uncaught InternalError: Timeout on I2C Write Transmit Mode 2
 at line 2 col 13
g|4,g|4,g,g])
            ^
in function "a" called from line 1 col 7
a(51,1);a(50,1);a(40,1);a(12,1);a(6,1);a(1,1);return{write:a...
      ^
in function "h" called from line 2 col 15
g|4,g|4,g,g])})
              ^
in function "connectI2C" called from line 5 col 49
    var lcd = require("HD44780").connectI2C(I2C1);
                                                ^
in function called from system
=undefined
Execution Interrupted during event processing.

Just manually executing load() again and voila - the LCD shows "Hello World!"

>load()
=undefined
Loading 4445 bytes from flash...
Running onInit()...

What's going wrong?