Will federated material be updated, after a reinstall?

I've set up a Lemmy instance and tested federation by commenting with my Mastodon account on the lemmy instance, which worked.

But I broke the test instance and had to start over (not even once).

The productive instance runs now, but after a few days I figured out that there is still the old post from the old installation on Mastodon and over Mastodon I can't see the new post and no new comments?

It is the same link (older Mastodon post, old Mastodon post, new Lemmy post), but the content is different.

• The post itself doesn't update (it is completely different)
• The comments don't update (different comments)

How to solve this problem? Is it even solvable?