After upgrading to 188.8.131.52 I am no longer able to rearrange the tabs of the open connections.
Have you also installed Windows 10 anniversary update? We have user which has this issue after the Windows update.
The same issue has been reported here - https://forum.devolutions.net/topic26461-unable-to-rearrange-tabs-drag.aspx
Other user has reported the issue after installing the Windows 10 Anniversary update. Have you installed this update?
Could you verify if you also have difficulty to drag email in Outlook as well.