Importing from three/examples/jsm/.../<module> causes bundlers (tested with rollup) to include the library twice (or multiple times).

For example, when doing import { OrbitControls } from 'three/examples/jsm/controls/OrbitControls', the bundler will follow the import and in the OrbitControls.js the imports come from ../../../build/three.module.js. However, there is no way for the (external) bundler to know that ../../../build/three.module.js is the same module as three.

A solution for this would be to treat the examples modules as external packages and import from three instead of ../../../build/three.module.js. This might break the rollup config of three.js, but it should be possible to tell rollup that three is an alias for the main entry point of three (src/Three.js).