We recognize that some users have experienced problems updating the firmware in their V3.1 Stock Spec, Xerun 120A V3.1, or Xerun 120A V3.1 1S. The origin of this issue is unknown at this time. However, if you are having issues with one of these models, please know that solving this is a priority for us. Please use the following link to submit the ESC for inspection by one of our certified engineers:

http://www.falconsekido.com/pages/hw-new-firmware-with-xerun-v3-1esc

We are committed to providing a quality product and will ensure that appropriate action is taken to remediate this issue once we receive your RMA application. 

Thank you for choosing HOBBYWING products.