While this started off well, it quickly lost my interest.
A researcher escorting an MTF team into a possibly hostile dimension is plausible, but when that researcher is a week fresh off from maternity leave, it seems like an unnecessary risk. We don't really get any regret or elaboration from her on this choice, and there's only three short lines of dialogue from her to her son.
There's no explanation of why the O5/Ethics Committee decided that the Lexicon was important - they didn't have any data on it beyond Alam speculating that it might be important/ a lock for some horsemen creatures they don't know about, but they decide that it's pressing enough for them to send another team into a hostile environment after two decades? L5-Beta even brings up the fact in-universe that the mission parameters/objective is extremely vague, leading to the expectation of some sort of reveal, but it's never brought up again. As is, it feels a rather contrived way for the rest of the story to occur.
I also found the little romance subplot between L5-Beta and L5-Gamma somewhat confusing- the latter wakes up and asks them out, and then gives them a flower and then… not much. Didn't really go anywhere. If it was to fill them out as characters, humanize them a little, it feels like an odd bump in the story's plot, and I feel that Beta's conversation with Hadid worked far better on that front.
On the note about characterization, the Hadid reveal about planting the Lexicon on Allegre entirely undoes his conversation with Beta earlier. We go from "guy trying to live up to the legacy of his not-so-dead mother," to "jackass who intentionally planted a dangerous device on another researcher, knowing it would attract dangerous entities to them". It removes any sympathy the reader could have for him, and leaves one wondering why he hasn't been fired for intentionally sabotaging the mission/trying to get someone killed.
Overall, I think this story as a result of its clear intention (though I may be mistaken) for more content on this dimension following this article up. Not all skips have to be one-shot self-contained stories, and sequels are always fun, but the combination of unreveals and plot contrivances make this unsatisfying.
