When a pass of CreateTransaction fails to select enough bitcoin to meet the nFeeNeeded the next pass through may select a far smaller collection of inputs.  Currently it will continue to use the old fee amount based on the larger set of inputs, which can cause a non-trivial over-payment.

This may be the cause of the behavior reported here: https://www.reddit.com/r/Bitcoin/comments/5ltw5n/bitcoin_core_v0131_sends_enormously_high_fee/

Long ago fixing this was tricky due to a catch-22 between signing the transaction and knowing how much fee was required.  But after #9465 the whole algorithm will run using a dummy signature, so when there is already a change output fixing up the fee after finding a sufficient transaction should be a matter of a ~2 line change.

{
    CWalletDB walletdb(strWalletFile);
    walletdb.WriteBestBlock(loc);
}
bool CWallet::SetMinVersion(enum WalletFeature nVersion, CWalletDB* pwalletdbIn, bool fExplicit)
{
    LOCK(cs_wallet); 
    if (nWalletVersion >= nVersion)
        return true;
    
    if (fExplicit && nVersion > nWalletMaxVersion)
            nVersion = FEATURE_LATEST;
    nWalletVersion = nVersion;
    if (nVersion > nWalletMaxVersion)
        nWalletMaxVersion = nVersion;
    if (fFileBacked)
    {
        CWalletDB* pwalletdb = pwalletdbIn ? pwalletdbIn : new CWalletDB(strWalletFile);
        if (nWalletVersion > 40000)
            pwalletdb->WriteMinVersion(nWalletVersion);
        if (!pwalletdbIn)
            delete pwalletdb;
    }
    return true;
}
bool CWallet::SetMaxVersion(int nVersion)