One thing you all could do is either try using a different browser or try clearing the cache on the browser you are already using. Beyond that, my thoughts are that it would be a good case for you all to bring to the User Support Desk or your Company Admins. It's hard to give a general fix just because there are many things that could be happening so working directly with your support channel is always a good step.
From your screenshot it shows you are using our new User Interface. It is still a work in progress and I think this might be causing your upload issue. If you can switch back to the other user interface, you may find you have better results.
If you don't know how to switch the interface, talk to your site administrator.