"Canon" is defined as what's widely considered official or authoritative:
https://en.wikipedia.org/wiki/Canon_(fiction)
It ultimately rests on what's licensed or not because non-canonical works are either fan fiction or derivative, i.e., works derived from what's no longer copyrighted. That means one has to deal with discrepancies, which is what I think is taking place in what you shared.
The problem is that we see those discrepancies even in what's considered canon. For example, for works in Tier I, the prequels reveal that WY knew a lot more about the aliens, but in the first movie, it's implicit that it doesn't know much. It's supposed to know much by the end of the first movie, but it either forgets it across almost six decades or knows about it after almost two decades, as seen in the game, and then forgets about what it knows again by the time the second movie takes place. And if a Twitter account referring to the game is included, can one also included Cameron's points in a sci-fi magazine about the second movie? In the latter, he states that the reason why the company could not find the derelict ship was because the beacon was damaged by volcanic activity. However, according to the game crew members of another ship deactived it.
Meanwhile, WY had to wait for the Nostromo flight recorder, as it either lost all data sent to it by Mother or never received them or Mother failed to send them or didn't want to to send them, while a privately owned ship in the game was able to find it, take the coordinates and visit the derelict ship, before infecting personnel in a company-owned space station. For some reason, the flight recorder was damaged after, and likely all transmissions on what was taking place on the rock and in the station and sent by multiple computers operating in ships and the station were not received by the company. Or they received them and lost them, or the computers chose not to send them.
For Tier II, several of the works state that multiple ships were visiting the derelict ship between the movies, but at least some of them also clarify discrepancies found in the movies themselves. For example, the second movie shows that the board absurdly didn't grant Ripley's request to have the location of the derelict ship investigated even though the accused (which itself is also weird because it's supposed to be only a board of inquiry) has the right to have a full investigation to prove her case. It turns out, according to one report, that the company deleted the coordinates in the flight recorder.
In addition, it was revealed that Nostromo crew members were filing reports and sending messages, like those from Lambert, and that even during the second movie, Burke was doing the same, even though it was implicit that WY was in the dark about the Nostromo or what happened to the colony or the expedition.
Meanwhile, some Tier III works attempt to explain other points in the movies, like the reason why the company has a bio-weapons division and special orders; it's because of what happened in the prequels. That means the company knew more than what it needed about the creatures, and more (like spores and all that), but could not any of them, which is why it waited until it detected the signal from the rock, and then had the Nostromo sent to investigate it.
It turns out that other adventures took place, similar to what happened in the first movie and in the game, and featuring even Ripley, who experiences amnesia so that she could not relate those additional stories to investigators. Meanwhile, just like in the other works, the ship and space station computers in these stories also work in a weird way.
And another work shows that the colony in the second movie, for example, was providing more than enough information to WY about the aliens, but probably not enough, which is why only a squad was sent: WY thought that only a few aliens, maybe two, were involved.
In any event, I think all my points involve the three tiers. The only thing I could remember about the rest of the works was the trilogy game, where in one cut scene it was pointed out that Burke was ordered by the company to secure the organisms for company labs. But that's necessary given works explaining similar in Tier II.
To conclude, the major problem looks like periodic amnesia experienced by WY, as coordinates are found and lost and found again, and computers not working until the third movie, where WY finally knows everything, but only about what happened on board the Sulaco. Or maybe more?