shadows of object

[Klas]

I have created two plane in xfrog, one with no rotation and one with a very small rotation about the x-axis. The first one has no shadows. Why? Tested with TG 1.10231 and 2.0021.
The object files are in the zip file in the attachment.

[Tangled-Universe]

hmmm...interesting. How small is the small rotation?