Has anyone ever gotten a “Input string was not in a correct format.” Error when trying to Check-In Files while working in a team? All I did was import like 15 models with materials and textures and it doesen’t let me push the changes. Need help please 
@ImPeQu Thank you for your report! We would like to look into this further, would you be able to submit a bug report using the form available here? Fortnite Creative
I have no idea how to reproduce this bug tho. I just imported a bunch of models, textures and materials so it might work for someone and not work for someone.
Update: I found the fix. The error was caused by UEFN not having acces to certain project files, It can be fixed by launching the UEFN .exe with Admin Permissions.