If the player does anything other than wait out the scoreboard and get started in the next matchmaking phase (e.g. go to orbit or just look at inventory) often the prior match will not be counted. Same kind of thing happens for Crucible and Gambit. Seems like your code to count the match (e.g. toward pinnacle) is not being called at the correct time, i.e. as soon as the scoreboard is displayed. This has been going on for a long time and you need to fix it--it's a stupid bug.