Lot deletes and system error

I have a problem where when I enter build mode either from manage worlds or live mode the whole lot deletes and I get a system error.

I have removed and turned mods off for the game. 
I have tried multiple times, and the error still happens. I load out to main menu without saving every time, but the error recreates itself no matter what I have tried.

I don't know what to do to fix this...

Have attached a screen recording of what happens when i go into build mode