Tried the following with Homeworld 1.3.3:

• Created a game
• Placed the portal
• Saved the game
• Saw that the portal was in the save game snapshot
• Loaded the game immediately

The portal was gone.

I have the same issue. The mod seems to be unplayable because the portal disappears every time.

Does someone know how you get a new portal? Is there maybe a LUA command?
Edit: Nvm, found it out. Type following into commandchat: "/c game.player.insert{name = "homeworld_portal", count=1}"

An alternative is to go into the recipes lua file and set the homeworld_portal recipe to true. Takes 50 alien artifacts and some brick. TBH when a decon robot nips off with your portal it should return it to you and not utterly destroy it.