Microsoft has released a second firmware update for the SP3 for September including the following:

• Surface Pro System Aggregator Firmware update (v3.9.650.0) improves booting time experience and enhances the system reliability while docked.
• Wireless Network Controller and Bluetooth driver update (v15.68.9030.41) improves the wireless network connectivity and stability.
• Surface Integration driver update (v2.0.1209.0) ensures when using a custom power plan that the selected plan will not revert to the default balanced power plan when installing a Windows Update.
• Microsoft Docking Station Audio Device driver update (v1.31.35.10) improves audio experience when no external speakers are connected to a Surface Pro 3 Docking Station so that Surface Pro 3 internal speakers are used.
• Management Engine Interface driver update (v11.0.0.1157) improves the system stability.