Can you check if any of the Windows updates has caused the problem? We know that sometimes Windows updates has an influence on the MST Hub behavior.
This is from Jan 16th updates
Intel(R) HD Graphics Family driver update (v10.18.14.4029)
Marvell Wireless Network Controller and Bluetooth driver update (v15.68.3073.151)
Surface Home Button driver update (v2.0.1179.0)
Surface Integration driver update (v2.0.1182.0)
Microsoft Docking Station Audio Device driver update (v18.104.22.168)
Here are the latest update packs for Surface