im sorry but you literally had to ignore the warning that shows when you open a project warning you about not downgrading, even offering to open a copy in that same window, then click ‘more options’ instead and click to actually convert in place, at no point did you think it might be worth backing up? at no point did you think what ‘preview’ meant and that at the very top of this thread it exlicitly says not to do this?? unreal has it’s issues but this is 100% user error