Server throws error on startup

I have recently just started getting this error and closes the server when i click okay. Hoping someone could help me troubleshoot what this means.The only stuff I have in my assets folder are car models, I have been adding some a few at a time and this has just started. I took the ones that I added before the error and deleted the chache but now its constantly throwing this error. I even replaced the server files and restored the backup yml config and still get the error.

Image of Error

This error means that you have a conflict in your assets folder. Check if you’ve tried to replace something and forgot to delete the previous file.

Hmm… Alright ill have to check what i have a duplicate of.