The problem still generally persists although the software-environment changed in the meantime:
- The Windows Creators Update was instal* led.
- I installed the latest Intel driver for the Intel HD Graphics 4000 (10.18.10.4653 from 7-April-2017).
Any help would be appreciated since the user-interface is hardly useable at all (in fact I have to use the iOS app).
Further observations:
Ever since the problem first occurred there have been about 2 Windows sessions that have not been affected by the problem and the user-interface response time was back to normal. Unfortunately I am not aware what circumstances might have caused this.