The Hromi Cluster is an unusual area, where each explored area seems to generate a random instance and mission when explored. Solo, the system seems to work fine. Unfortunately due to a bug it's nigh-impossible to complete any of these missions as a team.
These tests have been performed by three team-members, which I'll call 1, 2 and 3 for now. The following scenarios were tested and the results are as follows:
Scenario A: All three captains in the same instance of the Hromi cluster approach the same anomaly, and hit F to enter/scan it. Result: All three captains end up in different random missions and different instances. Each captain acquires only the mission relevant to the instance they warped into.
Scenario B: All three captains in the same instance of the Hromi cluster enter a previously-acquired Hromi Cluster system mission (owned by Captain 1) with the 'continue <mission name> (Captain 1)' button. Result: All three captains end up in the same mission, but in different instances. The two (captains 2 and 3) who didn't have the original mission acquire it.
Scenario C: All three captains in the same instance of the Hromi cluster send one of the captains into a pre-acquired mission first (Captain 3), before following with Captain 3's continue button. Result: Captain 3 ends up in one instance, while both captains 1 and 2 end up in a seperate instance together. As an additional bug, both captains 1 and 2 get a 'You are no longer in the team' message, and get kicked out of their instances after the timer runs out. This happens no matter wether they are actually in the team or not.
Several further attempts were made, but in only one of the cases did all three captains manage to arrive in the same mission and the same instance. In the on successful attempt, two of the captains got a 'you are no longer in the correct team' error, resulting in two of the captains getting kicked out of the instance.
In all of these tests, all three captains were part of the same three-member closed team.