I think the issue is probably due to ModSecurity. If you have cPanel for you host account, you can temporarily disable ModSecurity and then try again to save it.
If I enable the one that is disabled it works fine, the problem is I can't change position for the disabled one or add a new one where I need because of the error.
It is strange that I was able to add it with no problems and now something is blocking me.
Can you please share what to turn off in panel to make it work?