Thanks for your reply.
I am not able to show the rendering error in a screenshot because the problem is the not matching picture of the left and right eye in the HMD.
Some of the trees (about 10 percent) have a reverse lighting in the left and right eye (left half of the tree is rendered dark, right half of the tree is rendered bright for the left eye. For the right eye it is rendered vice versa: left half of the tree bright and right half of the tree dark.
The resulting effect is quite uncomfortable. This is with the standard setting stereo_mode_use_shared_parser = false
With the work in progress setting
stereo_mode_use_shared_parser = true
this problem does not show up (I do not use it regulary, I just tested the setting to check if the render error is related)
I did not have this rendering artifact in the previous open beta with the standard settings.
Hope this helps.