What setting do I change?
Its been a while since we used FPP on our server, you could try disabling the ghosting of props or mess with spam protection settings, explore a bit.
Hopefully someone who has FPP on there server could help you a bit more, otherwise if your still having problems maybe I can throw it on one of our test servers and see if I can help you figure it out.
Do you have a suggestion of a differnet prop protection mod?
If you looking for something simple, try Simple Prop Protection, there are others out there though, google around.