Can’t display file sets

Permalink
Hi,
I updated from 5.7.5.13 to 8.5.3 and also switched from PHP 7.1 to 7.3. It worked flawless.
There’s just one error I can’t solve. I can see all my file sets in the list and when I click on it, I get the attached error message: Call to undefined method Concrete\Core\Tree\Node\Type\FileFolder::getFileSetType()
Creating new file sets is not a problem, I just can’t click on it. And if I remember correct, I was never able to delete a file set. So, it could be an old problem which is just more prominent in the new version.
Can someone help me?
Thanks

1 Attachment