In the transactions list, if you right click a transaction and choose "view transaction details", the "Output index" listed in the resulting window is usually wrong.

With outgoing transactions, if you have a transaction with outputs like:

    vout 0: AddrA
    vout 1: AddrB, which belongs to sender
    vout 2: AddrC
    vout 3: <change>
    vout 4: AddrD

Then the output index as reported by the GUI will be:

    tx to AddrA: 0
    tx to AddrB: <transaction not listed>
    tx to AddrC: 1
    tx to AddrD: 2
    
With received transactions, the output index always seems to be reported as 0 in transactions I've checked.

I'd guess that rather than the actual vout index, some internal wallet index is being reported.

This is 0.13.2. I don't know when the bug was introduced.
continue;
                }
                CTxDestination address;
                if (ExtractDestination(txout.scriptPubKey, address))
                {
                    
                    sub.type = TransactionRecord::SendToAddress;
                    sub.address = CBitcoinAddress(address).ToString();
                }
                else
                {
                    
                    sub.type = TransactionRecord::SendToOther;
                    sub.address = mapValue["to"];
                }
                CAmount nValue = txout.nValue;
                
                if (nTxFee > 0)
                {
                    nValue += nTxFee;
                    nTxFee = 0;
                }
                sub.debit = -nValue;
                parts.append(sub);
            }
        }
        else
        {