Selling all of a stock not completing. Bug?

I'm seeing an odd behavior that I do not understand. Within my algorithm, if it is to sell a stock, it sells it all using:

          order_target(stock, 0)

I track in the log output all of the current positions and I see the amount of a sold stock decrease, but never go to 0. Watch symbol TAR decrease in amount to get stuck at 7834:

2003-05-15rebalance:218INFOExiting our positions on TAR, rank 0.813213528749
2003-05-16handle_data:142INFOCurrent positions: Symbol: EMT and Amount: 41666, Symbol: SFP and Amount: 44697, Symbol: USG and Amount: 47755, Symbol: PHS and Amount: 32657, Symbol: TAR and Amount: 40825,
2003-05-23handle_data:142INFOCurrent positions: Symbol: TPC and Amount: 5725, Symbol: SFP and Amount: 44697, Symbol: TAR and Amount: 40593, Symbol: PHS and Amount: 32657, Symbol: EMT and Amount: 41666,
2003-06-02handle_data:142INFOCurrent positions: Symbol: TPC and Amount: 40350, Symbol: SFP and Amount: 44697, Symbol: TAR and Amount: 31293, Symbol: PHS and Amount: 32657, Symbol: EMT and Amount: 41666,
2003-06-09handle_data:142INFOCurrent positions: Symbol: TPC and Amount: 69375, Symbol: SFP and Amount: 44697, Symbol: TAR and Amount: 22918, Symbol: PHS and Amount: 32657, Symbol: EMT and Amount: 41666,
2003-06-16handle_data:142INFOCurrent positions: Symbol: TPC and Amount: 152950, Symbol: SFP and Amount: 44697, Symbol: TAR and Amount: 7834, Symbol: PHS and Amount: 32657, Symbol: EMT and Amount: 16591,
2003-06-23handle_data:142INFOCurrent positions: Symbol: TPC and Amount: 144870, Symbol: SFP and Amount: 44697, Symbol: TAR and Amount: 7834, Symbol: PHS and Amount: 32657, Symbol: NEU and Amount: 11925,

Am I doing this incorrectly? I'm about to share this algorithm, but would like to make sure it's as bug-free as I can first.

Janene

I looked at this for a few minutes, but I don't think I can figure it all the way out without seeing the backtest. If you run a full backtest and look at the orders and transactions, it might explain what's going on.

TAR looks like a very thinly traded stock - sometimes with a daily volume of only 1200. My hunch is that you have orders that are open for days and are filling very slowly, and then you're issuing additional orders on top of the open orders, and that's leading to non-intuitive behavior. You might include a check for open orders, and if you find them, bail out or cancel them.

    # consider the status of filled orders  
    if get_open_orders():  
        log.info("Open orders! Run away!")  
        return