Comment 0 for bug 2033118

1. Open the attached file, "book2.epub" in the viewer.
2. Press Ctrl+t to display the table of contents.
3. Press Ctrl+f11 to enable the toolbar.
4. Click on the "Introduction" ToC item.
5. Click on the "Where to get help" ToC item.
6. Close the viewer, reopen the file.
7. Click on the "Introduction" ToC item.
8. Click on the "Where to get help"ToC item.
9. Close the viewer, reopen the file again.
10. Click on the "Introduction" ToC item. The "Back" button turns blue, but clicking on it yields no result.

Calibre version: 6.25,
OS: Windows 10 Home.