We found the problem for this issue!
We had layouts with no background color specified:
<layout width=“1920” height=“1080” bgcolor=“” schemaVersion=“3”
Even if a picture is/was set, if the field “bgcolor” has no numer (like bgcolor=“#000000”), you won’t be able to open such a layout in V2.0.0!!! And you have no chance to change the background color, because this was removed from the “Edit” menu.
So please make sure you have specified in all layouts a background color prior upgrade to V2.0.0!!
We had to replace the VMs HDD (with V1.8.12), specify a bgcolor on all layouts and re-upgrade.
Now everything works as expected.
Regards