Unable to click on users

Unable to click on users

I am an Administrator of our CRM account and I am unable to click on selected users under Setup > Users

Some of our users are appearing as 'undefined' and when I attempt to click on them the red bar across the top of the CRM page loads continuously. 

We've logged a ticket with support and have made no progress with the development team. It's been 4 days since the issue was reported, and our users are unable to work in the CRM. 

Is anyone else having this issue? Can anyone please help?