Thanks for pointing that out, it does seem like there is a slight bug in our ESC firmware that means it does not work properly with the latest version of arducopter firmware on the pixhawk. However the good news is that we now have a firmware fix for it.
All that you need to do is connect the ESC to your PC via the USB link board and load this firmware onto it. You will need to repeat the process for all 4 ESC on the quattro. You should find that it will now work properly.
Quattro-4in1-Pixhawk-Firmware.zip (4.4 KB)
To load the firmware, simply download the USB link software and once the application is open select the Update Firmware button and select the .hgm file included in the downloaded .zip file.
If anyone has any other issues please let me know.