Render switching changing look between keyframes

Hi. I am animating a short clip and the look of the animation changes after a certain keyframe:

One is keyframe 989 and the other one 990. I tried to check and un-check things and can not find what exactly is changing the look of it.

Here is the scene file. I already set the timeline to start and end in the keyframes that show the change of look.

Thank you

After hiding the background.001 and rendering again I found out It reduced the light changes (Sorry for the link, Can’t post More than 1 Image)

Thank you! but if you check the render then you get the red lines on the facade…thats the reason I have two grounds. One for the camera and one for the reflections. But its good to know thats what its causing it

Maybe I should find the way to have the reflection of one mesh and the look i nthe camera of another…with other technique that do not ruin the animation.