Ok I tried opening an even older backup of my wallet on 4.0.0 wallet GUI and managed to get the private key. However, what surprised me was that 4.0.1 GUI was also able to read that same wallet file and did not throw an exception this time. I might try to copy that older backup to my pi now to see if it also works out. the wallet is from September 2015. should I try the old wallet or still try to import the private key?
edit:
Just to be sure, I used the “back up the wallet” option on the 4.0.1 GUI in my laptop. It gave me wallets with different sha256sum’s than what I had from September 2015. I then copied those new backups to my Pi and so far it has been successfully downloading blocks. It sucks though that every time something breaks the block chain has to be downloaded from scratch. The block chain data structure should be built in a way that it could overcome problems and not require a full re-download at the sight of any problems.
