Shadow artifacts when I get very close to a sphere

When I get very close to a large sphere I will get these ‘squaring’ shadow artifacts.
I played with cascading shadows but have need been able to work around this.

This is clearly optimization but I am not clear on the exact cause :frowning:
Could someone tell me what the cause of this is, and possible how to prevent it if that is feasible? :slight_smile:

Many thanks!