Last week, one of my teachers almost lost his encrypted wallet private key. The cause of the incident was that the browser plugin of OKX wallet suddenly crashed during use, and Chrome prompted to "fix the extension" (many people may have encountered this situation, Metamask and other wallets also have this kind of problem). After clicking confirm, Chrome unexpectedly reinstalled the wallet and cleared the plugin cache. At this point, the wallet feels like it has just been installed and must be re imported with mnemonics to restore it. If there is no backup beforehand, the wallet and its assets will be permanently lost. Fortunately, this teacher is usually very cautious and has made multiple backups of mnemonic words in advance, which are stored separately. However, when he entered the mnemonic word, an unexpected event occurred: the wallet prompted that the mnemonic word format was incorrect and could not be successfully imported. After re entering several times, the plugin still prompts that the mnemonic word is incorrect. Although the teacher was a bit flustered, based on his solid knowledge of blockchain, he preliminarily judged that he had copied the wrong word or disordered the order when backing up the mnemonic. He attempted to write a script to restore by exhaustively replacing mnemonics, but his initial attempt was unsuccessful. I helped to contact @ Haiteng_okx of OKX wallet and confirmed that it is not possible to retrieve the wallet through the recovery plugin cache (mechanical hard drives may still have a chance, SSDs are unlikely), so the most promising solution is still to start with fixing mnemonic errors. In the end, after fixing a small bug in the script, I successfully recovered the mnemonic word that I had made a mistake with (a letter was copied incorrectly), and successfully restored my wallet. Everyone was happy. What can we learn from this event? The teacher's two summaries are worth remembering: 1. Disaster recovery measures should be practiced, not just on paper The mnemonic for this wallet has been backed up and copied multiple times, stored in different locations. However, there was no attempt to recover the wallet through mnemonic words, only a visual comparison of the correctness of the mnemonic words was made. At that time, I thought I copied it correctly, but in fact, one letter was wrong. If you try to recover your wallet using this mnemonic, you will find that the backup is incorrect. 2. Details determine success or failure A situation like this where only one word is remembered incorrectly can be easily fixed. But the repaired program did not consider the difference in case of Ethereum addresses, mistakenly thinking that it was not found. What could have been done in a few minutes ended up being delayed for three days, causing a lot of psychological pressure. My suggestion After backing up the wallet mnemonic words, be sure to check if the wallet can be restored correctly. When the wallet browser plugin crashes, do not easily click on repair. You need to first backup the plugin cache. 3. If there is an error in the backup of mnemonic words, do not panic. It is likely that 1-2 mnemonic words were copied incorrectly, and you can try to recover them through recovery software. I recommend open source: btcrecover github repo: https://(github.com)/3rdIteration/btcrecover Tutorial: https://(youtube. com)/playlist? list=PL7rfJxwogDzmd1IanPrmlTg3ewAIq-BZJ Safety is no small matter. I hope everyone can keep their wallets safe and not let hard-earned assets go to waste due to operational errors!