Since reinstall of Win7-64bit and DO9.5.6.x, I find only one level of back/forward. Can there be more?
My memory says yes. Neither HELP nor forum search seem to show.
Check the history settings in Preferences / Favorites and Recent / Recent List.
(At least, that's where it is in Opus 10. If it's in a different place in Opus 9, just type history into the filter at the bottom of the prefs window to locate it.)