Digital locks often have a manual override so flat batteries aren't too much of a problem. Of course you do have the question of security and pickproofness of the key lock.
I'm still wondering why combination locks aren't more mainstream.
ZQ how to get into your safe when the key fails is probably best reserved for the dark web or PM to known forum buddies. However my understanding is that some ancient dodgy safes might be best consigned to the scrapheap.
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