isort gets confused when working with git worktrees

If I work with git worktrees, isort (in the pre-commit hook) gets confused and identifies first party library code in the worktree as third party library.

I use

- repo: https://github.com/PyCQA/isort
  rev: 5.10.1
  hooks:
    - id: isort
      name: isort

What I do is:

git clone REPOSITORY.git
cd REPOSITORY
git worktree add ../REPOSITORY_WORKTREE BRANCH_WORKTREE
cd ../REPOSITORY_WORKTREE
pre-commit run --all

What it then does from:

import THIRDPARTY

import OWNCODE

when I run pre-commit run --all is:

import OWNCODE
import THIRDPARTY

or

import THIRDPARTY
import OWNCODE

Reproduce the report using the shown git worktree commands and pre-commit run --all with isort 5.10.1. Trace how isort classifies imports when invoked through the pre-commit hook, then verify that first-party code in the worktree remains separated from third-party imports in both reported outcomes.