This update is required for all IBKR traders who had upgraded to 4.0.11 and trade multiple lot quantity trades.
Bug Fix
- The upgrade to TWS API 10.37 had a side effect that was not mentioned in their release notes, which could cause trades that fill partially to overfill, opening both the partial fill and the original quantity combined.
This could cause a larger than expected trade to be opened. A fix has been implemented in version 4.0.15
UPDATE: 4.0.16 is now available with an additional change to ensure the same fix is applied to manual and scheduled closing trades at IBKR.