Style Transfer produces white noise

Hi!
I’m playing with Neural Transfer Using PyTorch — PyTorch Tutorials 1.9.0+cu102 documentation
Running this demo on colab (torch version == 1.9.0)
I changed images (style is https://raw.githubusercontent.com/jcjohnson/neural-style/master/examples/inputs/starry_night_google.jpg and content is https://raw.githubusercontent.com/jcjohnson/neural-style/master/examples/inputs/hoovertowernight.jpg)
Also set num_steps to 1500
After a while (about 1400 steps) image degrades to white noise

Below is Content and Style losses graph to show this.

Why is it happening?