I have the opera://bookmarks tab open with the "Other bookmarks" folder open. If I reload the page, it still stays at "Other bookmarks". If I leave the tab open and exit Opera and open Opera back up, when that tab loads again, it's still on "Other bookmarks". So, that seems to be working fine for me in those cases.
Could you give more specific details on how and when you're opening the bookmarks page and if you're using the URL opera://bookmarks or something like opera://bookmarks?id=2?