I am totally blind so am not sure where focus is landing, however, when I press Tab or use the arrow keys, no accessibility feedback is provided about moved focus if this is occurring.
Use F10 at any point to take you back to the main menu. Then F10 again to return to the document text.
F6 cycles through the GUI control elements (Main menu, toolbars, status bar, sidebar, etc.) Specific order will depend on what object(s) have focus on the document canvas.
So, use the F10 to return to a known position.
I can confirm that I am able to use the keyboard shortcuts you suggest to move focus off this element. However, I am not sure what the "Option pane" is that NVDA describes. In most of the toolbars, I can use the Tab and arrow keys to move around, however, in this instance, none of these keys do anything when this pane is focused. Is this something with functionality that NvDA cannot access? This is a default install so pressing F6 three times should cause your focus to land on this if you have fresh preferences.
*** This bug has been marked as a duplicate of bug 105518 ***