I can't publish or launch a session in my map due to Im getting errors on having no shaders, though the map is perfectly normal. Never did anything but uefn.

@2AMBatmanBessy Thank you for your report! Can you please re-post using the “New Issue” option on the Issues and Bug Reporting forums? Posts with this feature are connected directly into our development team so we can quickly get to them!
For more information, such as how to get the reference ID, please check out the article here: https://create.fortnite.com/news/using-the-creative-and-uefn-bug-reporting-form

UEFN has issues with Onedrive.

Move your projects out of Onedrive, you can then use Edit -Editor Preferences - Settings to add a project location to point to the new directory.