Base Upload Limitations
Bases are far more limited when uploading for others to see than they are for just you.
You can have as many bases as you want on a single planet, but you can only upload one of them, any others on the same planet that you upload will overwrite the former.
This also counts for bases you have on that same planet on different saves.
It is not one per planet per save, but 1 per planet per player.
To upload a second base on the same planet and have them be visible by other players, you must upload the second on a different account.
This works for different PSNs as well as different steam accounts.
This is the primary reason that the UAS will have 2 Stasis Device Systems so that one player can upload over multiple difficulties.