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.

{
                if (mapWallet.count(txin.prevout.hash))
                    mapWallet[txin.prevout.hash].MarkDirty();
            }
        }
    }
    return true;
}
void CWallet::MarkConflicted(const uint256& hashBlock, const uint256& hashTx)
{
    LOCK2(cs_main, cs_wallet);
    int conflictconfirms = 0;
    if (mapBlockIndex.count(hashBlock)) {
        CBlockIndex* pindex = mapBlockIndex[hashBlock];
        if (chainActive.Contains(pindex)) {
            conflictconfirms = -(chainActive.Height() - pindex->nHeight + 1);
        }
    }
    
    
    
    
    if (conflictconfirms >= 0)
        return;