Not a bug. It's working correctly.
Team 1 starts with a full clock (I think it's 8 minutes but could be off). You reach the bridge with 1:30 left. When team 2 starts they should of started with only 6:30 on the clock so all they have to do is get as far before the clock ends. Now it's completely possible that there is a bug and team 2 is not getting a shortened clock. I haven't PvP'd since 1.4 so bugs are possible but since the last PvP changes months ago it always has been as long as team 2 go to the same point before their clock ran out, they won.
One more time, people. Round 2 only starts with a shortened clock if Round 1 attackers reach the datacore. Otherwise, Round 2 will be allowed to go the full 7:30.
This sounds like a bug where in Round 2 the attackers make it as far as round 1 attackers but more quickly, triggering the end of the match (good so far...). However, it's treated as a tie and victory is awarded to round 1 attackers, who have the most kills because they were on offense for longer (this is the bug).