@Pluvinarch

This is probably the most likely explanation. It's the only thing that makes sense fore everything if you think about it.

A possible explanation...

Opbot may be old, really old. He was a medical bot from the Mezari empire, working on the Argosy. Then he went nuts and was charged for murder. He gets out of the Argosy ship who was headed for Auriga and goes to a prison facility nearby. Lucky for him, because the Argosy crashes on Auriga. The Mezari, or someone (the DotE Album author?) sees that a super powerful cryo-coloniser like the Argosy couldn't even land on the planet and decides the place is well protected and therefore a different method of colonisation must be chosen, which means sending prisoners there. Opbot then goes to the Success with other prisoners and, as planned, the Aurigan defense system shoots the ship. Opbot and other crew members survive through the escape pods. After DotE, Opbot works with the surviving Mezari who will become Vaulters until he gets crazy again and is shut down.

Flash forward to Endless Legend. Auriga is now dying. The actual generation of Vaulters find Opbot and decide to turn him on again. He is trying to recover his memory. Not everything comes back, it is all selective. The Vaulters find the remains of the crashed Argosy. Opbot, since he worked on that ship, remembers it. He didn´t see the Success (maybe it was totally destroyed and only some very small pods from it made to Auriga) so he doesn´t remember the DotE part of his past.

Argosy was a Mezari colony ship while the Success was a Mezari prison ship. What probably happened was the Argosy went first and crashed, so the Mezari thoght it would be good to send prisoners there in the Success, which then crashed. The people from both ships probably eventually intermingled creating the vaulters.

So I see now that it's explicitly said in ES2 that the Vaulters come from convicts and prisoners. So now the question would just be what is the difference between the Argosy and the Sucess?

TartarusMkII wrote:

Also, I understand this text was voted on, and is Opbot's description in ES2:

Operating a recon mission, Academy scouts were exceedingly surprised to discover that a promising species of pre-sentients had, within the span of a few years, gone from huddling in mud hovels to trying their hand at space exploration. Investigating this extraordinary technological leap, the scouts eventually met a battered robot who introduced itself as Opbot 0V8. It explained that after drifting through space for quite a bit and subsequently crashing on this planet, it was rescued by the natives. As they were friendly but of limited intellectual reach, Opbot decided to help them "get there faster" --but declined to share more details on the process.

So then, was he not on Sucess? Does that mean, then, that the Vaulters are not from the Sucess?

I think that refers to the events after ES2 Vaulters introduction, when Opbot has gone missing again. We voted for that backstory, apparently he helped yet another race to reach the stars.

Success was a prison hulk and Argosy - cryo-colonizer fortress with library full of valueble information. So those are two different ships. Besides, you can see Success destruction in DotE trailer. And I doubt those are only two mezarian ships that ever landed Auriga, that once was major Endless settlement. Because we know that Vaulters came from Mezari, and Forgotten came from Vaulters, yet it's not clear were Roving Clans, Ardent Mages, Dorgeshi, Sisters of Mercy and other aurigan human races came from.

Opbot was a prisoner aboard Success, presumably for murder. According to his memories in EL, he once was a mezarian "Operation and Medical Procedures Robot". But during some strange event, when his surgical facility was overrun with wounded after Groits attack. He had to witness too many bloodshed and somehow gone mad, and went on a murderous spree with his scalpel. In DotE he claims Groits reprogrammed him to do that.

EL quest text indicates Opbot had information about legendary Argosy and its catastrophy in his memory banks, so he shared his knowledge with Vaulters.

Update: 

So, Emaps the Cosmic Spacecat of Discord was able to find a list of quest dialogue on one of the many wikis that I wasn't able to find. Thank you Emaps! https://endlesslegend.gamepedia.com/Quests

"Stalking the dimly-lit corridors of the "Argosy" has brought back all the horrors in my mind. I remember odd details - desperate hands gripping a bulkhead, a woman scrabbling to get away into a vent, staring at a bloody scalpel with gleeful fascination. The memories stun me immobile, unable to speak."

So now we know that the lore of the two games, developed side-by-side, indeed contradicts themselves, that is unless the Argosy and Success are the same thing. So now we wait for clarification! I'll update the OP when there's more, thanks!

Isn't Argosy just a renamed Success? There weren't many Mezari ships that have fallen on Auriga. Only Success. They just frogot about Success and then had to look for in in EL.

Yet they do look different...