Been struggling with this one for a while. Maybe someone else here may have experienced it and could give insight on causes and hopefully a way to resolve.
In the screen shot above. On the left there is a quadrant of ceiling that is vertical and intersecting the light fixture. It's visually wrong. It should be positioned flat similar to the quadrant on the right. The blue outline where the object is in actuality is correct. If I switch to preview mode it shows up fine. However on both fast and accurate as well as final rendering output it tilts up for some reason.
It only does this for a certain section of the animation. There are no keyframes related to this and it is somewhat random in it's occurrence in the timeline with each successive play. The other ceiling quadrants which are instances of this part do not show this behavior. Also I have since suppressed this part. Re-imported it as a separate group/entity re-positioned it to the same location. It was fine for a while and then all of a sudden the new part started flipping up.
Another image showing the issue. In the active window rendered with accurate. The ceiling is flipped however the selection outline is not.