I noticed this prior to yesterdays patch of 16.12.15
Sometimes the scoreboard does not show all players.
Ive had an obvious bug in exec where the team showed 3 on the SB but we had a full team. This happend a few times and Ive also seen others comment about it.
Outside of exec I have only noticed this once on a SW server. The SB showed 6v7 and I commented on it, that we might want to do the reround also with 6v7. Someone answered that its all fine and then I counted players on my team: Actually 7, but only 6 on the SB. I did not count enemies however.