So I shut down Bitcoin Core. I backed up this new Wallet.dat file, then I copied over my existing wallet.dat file to the Bitcoin folder. Computer says " Do you want to replace the existing wallet.dat" and I say yes.
Did you do all of these within a minute?
Because Bitcoin Core will take a few seconds to shutdown before it fully shuts down.
During that time, it may have "
redone" what you've done in the copied-over wallet.dat to the "
everyday wallet" because "
releasing wallet.dat" is in the last part of the shutdown process.
I can only guess since what happened was bizarre if there's no human error involved.