Shift from "He" to "His group" to "They are" in three sentences.

Hi all,

Reading a document today, I noticed an interesting shift in the subject
of three consecutive sentences concerning a scientist and his
colleagues.

The first sentence started with "He has been investigating [field of
study]." The second began "His group has begun [related activity]." The
third, "They are also [other activities]."

I'm not sure if this is right, wrong, or sort of in the middle. The
"They are..." obviously refers to "His group" in the second sentence,
and if somebody said "His group of bandits has arrived! They are going
to ransack the palace!", I wouldn't think twice. But this seems sort of
jarring, probably because we're jumping from third-person singular to a
group to third-person plural in a really short space.

Is this okay? Or does "his group" need to be followed by "it" (one
group) as opposed to "they" (group of individuals)?

- Matt

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