While dragging and dropping a big file then max allowed (in file manager), an error message pop-up. Clicking ok leaves loading animation. Try adding another big file leaves two loading images and keeps increasing as you try adding more big files.

1. Go to a course -> Forum
2. Create a new post
3. In attachment area see if 'You can drag and drop files...'
4. Change the course settings to set max file size of only 10KB
5. Go to forum and drag and drop a file more than 10KB
6. Error message will be displayed, click ok
7. Loading image remains, try adding another big file
8. Error will pop-up again. After clicking ok, there are two loading images.