Git checkout generates an error on --assume-unchanged files

After I run git update-index --assume-unchanged path/to/file on a particular branch, I'm unable to switch branches using git checkout.

It throws the following error:

error: Your local changes to the following files would be overwritten by checkout:

      path/to/file

Please, commit your changes or stash them before you can switch branches.

Aborting

But both git diff & git status tells me there is no difference & there is nothing to commit/stash.

How do I switch out of the branch?

Is there a better alternative to git update-index --assume-unchanged (other than .gitignore, because I don't want it to be ignored)? (Same as question 2 @ git update-index --no-assume-unchanged doesn't work)

After some amount of use I now prefer git update-index --skip-worktree which is a much better alternative to the git update-index --assume-unchanged.

Check out Difference Between 'assume-unchanged' and 'skip-worktree' for further information.

I also am planning to check out the method specified in this answer to git assume unchanged vs skip worktree - ignoring a symbolic link, which seems to be more defensive approach.