Let's think about Ven's claim that he was summoned into the building by Ava. My understanding is that one of the following has to be true:
- He was really summoned by real Ava
- He was really summoned by fake Ava
- He is lying about it
- It is a false memory installed by the killer
We can rule out lying, because why would he mention the building at all? Real Ava is also unlikely. Even if she had some reason to talk with Ven, she wouldn't choose Gula's hideout as the meeting place. If it was fake Ava, why was it done? It can't be related to the murder, because the murder was not planned. The killer had no way of knowing that Strelitzia would come to the building at exactly that time.
So, false memory seems to be the best explanation. The most likely chain of events is: Ven by conincidence walks by the building when the murder is happening. He hears noise, goes in to investigate, sees the body, freezes/faints, and is caught by the killer. The killer disguises himself as Ava (or was already disguised, it makes sense if Gula was his intended target), erases Ven's memory of the events, gives him the false one, and proceeds to lead him out and name him as a replacement union leader.
There is surprisingly little new information in the whole update, only the fact that Ven saw the murder, and confirmation that the Ava Ven met is a fake one. Real Ava was on the hill with Luxu at this time.
Now, please point out if I have missed something!