When I have had a failed FW update it did the same thing. My fix has always been to start it again with a fresh battery, AC boot only, bin on card, and placed it in a room were I didn't have to hear it. It took longer than normal to update, but it eventually did.
The only oddity I once had was; it kept beeping for a long period, then after that long period I turned on the RC and it completed in seconds. I can't say for sure that the RC played a part in the eventual success, could have just been coincidence, but worth the attempt.
Good luck.
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