Screen options & help tabs not working

Just wondering if anyone can help me. The screen options & help tab (top right) of an important wordpress site recently stopped working. I know that Wordpress support will advise me to turn off all plugins and to revert to a standard theme to check if it's a Wordpress problem. I'm sure it's not and that it will be a theme or plugin conflict. The site is quite complicated and uses a theme + several vital plugins...including WPMUDEV.

Can anyone advise a work-around - perhaps a way to default screen options to 'open'?