How the tank spawn bug works and why it's possible your team lost because of it:
1) What it is:
The tank spawn bug is where one team will get the other teams tank spawns
2) How it works:
Until you kill the enemy's original tank spawns, you will not be getting new tank spawns. I'm not 100% sure if you cap the flag closest to the base if it will correct this bug, but I do know that if you lose your team's original tank(s), you will not get another until you kill the enemies original tank(s). You can kill the extra tanks spawns they get all you want, you'll still not get your tank spawns back. You have to kill their original tank spawns.
3) Why this is game breaking:
It's fairly obvious. If your team can not kill the enemies original tank(s) that spawned at the beginning of the game, and your friendly tanks get killed, it now becomes a 4 v 0 where it's neigh impossible for the team to get its act together to get the original enemies tank(s) and still stand a chance at coming back.
I still don't understand why DICE has yet to fix this bug. This bug is so game breaking that the bug fix should be a patch by itself.