I think the problem likely is this.

If there is one seat available, and a plat+companion is next in the list, you don't get the seat.

Now, the 'correct' thing to do here is probably not give the seat to anyone. But what I suspect happens is that since the EUA can't award the seat to you, it goes down the list until it finds a plat traveling alone, and gives them the seat.

Then later, if more seats open up and there's one seat left, you get skipped AGAIN and another single plat gets the seat.

Repeat for each time the EUA processes until there are no seats left in F.

Software probably needs to be fixed so that if there are 2 plats at the top of the list, and one seat available, the seat stays open.