Eject device on PRS-T1 gives WERFAULT

Calibre version 2.35 (64bit) on Windows 10 Home.

After having formatted my PRS-T1 and sent a bunch of new books to it, wanted to eject the device. Using the Eject button in either of the 2 device buttons on the menu bar.
- Error message appears: WerFault.exe - Application Error ...
- Click OK to close the error message
- Another error message appears: caliber-eject.exe - Application Error ...
- Click OK to close the error message
- Again an error message: WerFault.exe - Application Error ...
- Click OK and then no more errors.
- Have to use "Safely Remove Hardware and Eject Media" to eject the reader and remove USB cable.
- After this the Reader seems to work ok.

This problem is persistent. Tried to connect and eject a few times. Closed Calibre in between. Problem remains.

Yesterday the problem did not occur when I was using version 2.3. This morning I upgraded to 2.35.

Any help is appreciated.