Black tiles in my animation

Hey Guys,
i have a big problem. I rendered an animation for my customer. The animation is 300 frames , rendered with Optix Denoiser and 25 fps. At the beginning everything is good and nice, but at the end the final render shows this black tiles and i dont know why.

Samples 100 , resoulition 1080x1080 200%
hope you can help me, thank you very much