Please do a test for us, so we could know if it is the problem of your ESC.
Here is an instruction:
1.Turn off the remote first.
2.Leave the board alone for about 15 minutes.
3.See if the board is able to turn off by itself. If the board doesn't turn off after 15 minutes, that means you would need a new ESC.
For diagnosis purpose, please share a video that you are trying to turn off the board to us via G Drive, Dropbox , YouTube private video, etc..
Please kindly be reminded your test video is a must for us to arrange accessory replacement under warranty.