Error Messages Launching any UEFN Project

The manipulation does not concern a software problem which crashes when modifying a project.

I didn’t have the problem you described but while doing a search I found this post which dates back a few days :

https://www.reddit.com/r/FortniteCreative/comments/1gi5wcj/uefn_crashes_when_i_open_a_project_after_the/?rdt=41339

You can also try to check the files from the epic game launcher

Hoping that it can help you.