Originally Posted by WS64
This might be the reason.
I turned it off again because I thought this might be the reason for the slowness when connecting to Calibre...
Well, it sort of is. During the automatic sync, the driver is fetching the state of all the books on the device and in the library, comparing it and then updating the shelves as appropriate. One bit of that is horrible and I need to revisit it to see if I can speed it up. But, with shelf management configured, it will never be as fast as the old driver.