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 (nOrderPos == -1)
        return;
    mapValue["n"] = i64tostr(nOrderPos);
}
struct COutputEntry
{
    CTxDestination destination;
    CAmount amount;
    int vout;
};
class CMerkleTx
{
private:
  
    static const uint256 ABANDON_HASH;
public:
    CTransactionRef tx;
    uint256 hashBlock;
    /* An nIndex == -1 means that hashBlock (in nonzero) refers to the earliest
     * block in the chain we know this or any in-wallet dependency conflicts
     * with. Older clients interpret nIndex == -1 as unconfirmed for backward
     * compatibility.
     */
    int nIndex;
    CMerkleTx()