Startopia multiplayer crashes to desktop

Try removing the only mod (the "glowing ore veins mod") you have, just to check if does not really cause the crashes.

Also, it might be the case of the ol' Savegame bloating. Try the Unofficial Skyrim Patch (UKSP). Among its fixes are:

• NPCs will no longer drop weapons or shields as separate objects, as these are never cleaned up which greatly adds to save bloating and litters the gameworld (the items will still appear to be dropped, but will access the corpse's inventory to be taken and be cleaned up with the corpse if left)
• Ash Piles, Ghostly Remains, Ice Piles and Wisp Cores will no longer permanently remain and bloat the save file (they will either disappear on exit of the cell or when the cell resets)
• The torches on sconce activators will no longer duplicate-in-place (also adding slightly to bloat) when their cells respawn; the duplicate(s) would remain when the player picked up the newest torch (note that this fix is not retroactive for existing duplicate torches; simply open the console, click any duplicate torch and enter delete to get rid of it and no new ones will appear)

The Unofficial Skyrim Patch is a comprehensive Skyrim bugfixing mod that could also help solve other potential CTD issues. Full list of its fixes here.

The mod, Possessive Corpses, has a 'less arrows' module, which has this feature:

The amount of arrows per cell (not counting the ones in inventories, droped or attached to actors has been reduced from 15 to 5.

From the mod's description:

Missed arrows aren't deleted by the game, but there is a max number of arrows allowed in the world. Once you (or another actor) fires an arrow pass that limit, the first one being generated is removed. This way, arrows can last months but won't ever pass the limit number. In my game that number is 15, but Those of you with ultra settings may have a greater number (I really don't know what controls this number and if can be changed at all).

I'd use only the 'less arrows' module of Possessive Corpses with UKSP (as the other features of Possessive Corpses might overlap with UKSP).

Remove the duplicate buildings.

Then make sure that everyone's basic needs can be meet (hygiene, food).

You may need to rebuild and reorganize a lot of rooms and hire aliens to operate them. This is typical if you have a lot of new aliens to look after now that you've defeated the AI.

Also, the visitors often get "stuck" when they want to go to a different manager's section and they cannot travel there. Trying to take over another section (above or below) will often get theses aliens moving, as they can finally path to where they want to go while a section door is open between your part of the station and the other manager's sections. Unless you are rolling across the entire level, you will often "lose"/anger many of these stuck aliens who cannot reach their desired destination and refuse to chose something suitable in your sections instead.