I make a change in the submodule and commit it, come back to the parent repo and on checking git status, expect it to say there are changes in the submodule, but nothing is listed. The parent repo doesn't point to the latest commit of the submodule either.
I have intermittently experienced the issue you describe and the following commands have worked for me
git rm --cached path/to/submodule
git restore --staged path/to/submodule
git status should now show the new commit in the submodule