looking at the logs it could be DX12 (directx 12 Ultimate Windows drivers) with a problem try DX11 setting
on Fortnite settings and the UEFN setting to -d3d11 to turn off DX12
and make sure you latest drivers
RESOLVED: Known issues with NVIDIA 576.02 drivers on RTX 50-series GPUs | Epic Developer Community
Unfortunatley you may need to reload a new version of UEFN if verify does not fix this.
Make regular Zipped backups of your project as you are not using Revision Control