I'm running 1.12 and I'd like to say that I have not had any problems loading a Config File to restore a previous configuration.
Matter of fact, with each of the previous versions, I've not had any problems.
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Then again, for those having problems, Before updating the Firmware, have you tried
1st - Disable the Wireless
2nd - Disconnect everything from the router (except your main system)
Then after you successfully flash your Router, Login and try to Load and restore the Config file.
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This is the proceedure I follow each time.