Serial1.write disconnect USB console

Hello !
I'm trying to control a SerialMP3 board but each time I send a command my espruino WiFi is disconnected from the USB console

var id = 1;
Serial1.setup(9600);
Serial1.write([0x7E,0xFF,0x06,0x03,0x00,­0x00,id,0xEF]);

Any idea ?