Magot, zflyer wrote if the first post of this thread:
Known Problem: Shadow flicker and disappearance
The problem afflicts mainly the Do24T but is present to a lesser degree in the other versions.
The problem may be due to the fact that the shadow shapes are too complex and need to be simplified, or that they include open vertices. I advised him to get in touch for advice with Birdman who knows very well how to deal with this kind of problem.