I've been testing this extensively in the past week as I'm keen on it too. It has actually been fixed (I'm fairly sure it was broken at one point), and it's just a graphical display issue now. It affects both 5+ INF and 5+ REP missions. So it is fine to do these missions now, even though it looks wrong when you complete them.
On the other hand, I've been doing passenger missions for INF, and according to my logs half the time the influence/rep is only awarded for the faction you deliver to, not the faction you pick them up from.
As an additional twist, the UI shows the pickup and delivery faction reversed when it does actually work.
Here's one that did work:
{ "timestamp":"2022-01-24T11:26:59Z", "event":"MissionCompleted", "Faction":"Alliance Vanguard Crew", "Name":"Mission_RS_PassengerBulk_name", "MissionID":840038984, "DestinationSystem":"Ronemar", "DestinationStation":"Lattu Bay", "Reward":10000, "FactionEffects":[ {
"Faction":"Federal Acquisition Corp", "Effects":[ { "Effect":"$MISSIONUTIL_Interaction_Summary_EP_up;", "Effect_Localised":"The economic status of $#MinorFaction; has improved in the $#System; system.", "Trend":"UpGood" } ], "Influence":[ { "SystemAddress":1183967810114, "Trend":"UpGood",
"Influence":"+++" } ], "ReputationTrend":"UpGood", "Reputation":"++" } ] }
and here's one that didn't:
{ "timestamp":"2022-01-24T11:33:02Z", "event":"MissionCompleted", "Faction":"Alliance Vanguard Crew", "Name":"Mission_RS_PassengerBulk_name", "MissionID":840039074, "DestinationSystem":"Ronemar", "DestinationStation":"Mercer Silo", "Reward":10000, "FactionEffects":[ {
"Faction":"", "Effects":[ { "Effect":"$MISSIONUTIL_Interaction_Summary_EP_up;", "Effect_Localised":"The economic status of $#MinorFaction; has improved in the $#System; system.", "Trend":"UpGood" } ], "Influence":[ { "SystemAddress":1183967810114, "Trend":"UpGood",
"Influence":"++" } ], "ReputationTrend":"UpGood", "Reputation":"+++" } ] }
Source faction gets wiped, mission rewards screen only shows the destination faction.
It doesn't seem to make any difference whether it's an INF++ or an INF+++ mission. I haven't pinned down the exact cause yet.
Short summary: don't waste time doing passenger missions for influence.