What I have experienced is this:
On ‘Unification Day’ I wanted to travel to the pre-planned No Man Sky celebration organised by the players of the game. This took place on a certain planet only in Euclid Galaxy. The first galaxy was chosen as everyone will have started in that Galaxy.
I left Euclid long ago (Normal Mode) and so my only option was start a new save AND OR use Creative Mode. Why Creative mode? Because I had instant access to all Glyphs, recipes etc so could equip my ship for portal travel immediately.
Those players who have moved on to later galaxies, currently can not return.
BUT you can start a new game save slot for the mode you like to play, Normal, Survival or Permadeath or Creative and visit Euclid Galaxy.
Until we have a means to travel across entire Galaxies by ‘teleport’ visiting later galaxies can only be done by using ‘old’ game saves.
On Unification the Portal Address for the planet transported the player straight to it. BUT Each portal address contains a planet I.D for the particular planets in any given system. Without explaining in too much detail, simply put, if there are six planets in a system, each planet will have a unique I.D 1 to 6.
If you put in a random address for a planet never visited before, you may end up on any one of the planets in a system. The game is designed this way for exploration and I guess anticipation. Until perhaps we have upgraded ‘tech’ to be more precise.
You will be in the system you chose but may not be on the planet expected.
You would have to actually leave that planet and fly to the one you want. To do that means using any unclaimed home base base (on the portal planet) temporarily to teleport from your current system. OR the longer way would be to Waypoint the new portal discovery (now in your list) - return back through the portal and hop to your destination system by star system across the galaxy.
I guess, if you do ever encounter the red warning ‘Access Error!’ using portal travel you know you will get a random planet. In that instance, you could import the address a few times changing the first glyph (which I think is the identifier) but it is a random choice.
One other thing to note is sometimes bases do not update from the server until you visit a third party base then return BACK to the base that was not as expected. In this way the cache is ‘flushed’ and base you had expected should re-appear.
It is a long explanation and you may know some of this. But hopefully it might offer a possible solution.