File getting (randomly) deleted on build

Hello there,
I am actually struggling with a weird yet annoying problem.

When I build my site, if in the destination folders some static assets already exist, these are deleted instead of being recognised as identical.
As a result of this, I kind of entered in a sort of loop which it was possible to solve only by removing the all build folder’s content.

It would lovely if the dev team could look into this.

Andrea