Did the Engineers knew what happened in LV-223?

Maybe they thought the base was lost due to the black goo killing almost everyone.

Janek mentioned how the Engineers were smart enough not to create weapons of mass destruction on their front door so they made it on a separate outpost (Lv 426)

Good question. Maybe they knew about 223 but not the whole story. Sort of like how we know we have a space station but aren't privy to everything going on with it?

plus that was 2,000 years ago remember

Makes you wonder why they didn't plan a second expedition to earth and a fresh batch of mutagen goo for the ride.  I think that it's just one of those loose ends that was glossed over.

Loose end? Has to be.

Logically, in a facility of that nature, Something Happens and at minimum a Contamination Beacon would go off. There'd be some kind of automatic message sent to whomever are the higher-ups.
There'd be no efforts at rescue, obviously.

As for why they didn't try to attack earth using another base, perhaps this was the only facility capable of producing the Black Liquid as well as being the only storage depot for it.

Judging by the Engineer reactions:

1) They recognize the Juggernaut ship

2) Applaud to it like they where expecting it for a long time

3) They expect it to descend or dock to the hovering scorpion

4) They are idiots gathering in ten-thousands under a black goo bomber. Looks like sheeps preparing to die.

Maybe you can indirectly somehow explain if they knew about the LV-223 accident by the above reactions.

Perhaps the ones who left "Paradise" for LV-223 were trained (military) pilots (who could fly the juggernauts) and scientist (who could develop the biological weapon)? Presumably, all their juggernauts left for LV-223 - and never came back (because of the outbreak). The "ordinary" engineers on "Paradise" would therefore not have seen a juggernaut for 2.000 years (many generations)? Also, the engineers don't communicate with each other over distances since they don't have to with their fast space ships? So, the engineers on "Paradise" didn't know exactly what had happened - the engineers sent on the mission to exterminate the human race (who started to become a threat) simply didn't return?