Yeah, there seems to be a few bugs in V2.0. The previous version was more stable.
Regarding your empty scan preview, I sometimes see this when the scanner has picked up "noise" from the area behind the turntable. The preview hasn't disappeared though, it's just gone off to one side and zooming out reveals the preview again.
I fixed this by placing a black sheet behind the turntable to stop it picking up anything that shouldn't be in the scan.