Edit: Actually, I've been able to recreate this by trying to print my own page of paper wallets from bitaddress and messing with the scaling factor up to around ~150%. It does indeed only cut characters off from the start. And actually, bitaddress only generates EC multiplied compressed keys, meaning all the keys will have the prefix "6Pn". So OP is only missing a single character from each key, in the 4th position, which will be between the characters "M" and "Z". Given that "O" isn't used in Base58Check, then that only leaves 13 possibilities for each key.
Hey so I still have problems with the private key. I've tried to start with 6Pn(A-Z) but it says that all of those are invalid keys. It is the key and not the pass phrase because I made a new wallet and put in the wrong phrase and I got a different message. Could it be that the third digit "n" could be different as well. I made the wallet in 2020 if that has any meaning. Any bright ideas
?