Do you have a demo or log of what happened here? If you joined, got placed on one team, then people from the other team disconnected, you'll get autobalanced. Isn't it better to be switched after 1 sec (so you don't have any real commitment to the team) than to be switched after playing on the team for a while?
Well, if you type "join a" you are using old pre-autobalance mechanism that will tell which team to join basic on amount of people, right?
Isn't that if autobalance is on, still it won't get to choose where you join? I think this is the case: Old mechanism works, puts me in the team, then autobalance goes "it's wrong" any puts me in another team.
If I recall correctly, this was on speed tho, so could be that people just left. But since you added this mechanism:
1. I get switched all around if I don't play from beginning for rest of map pretty much (since i'm generally better than pub people).
2. If I play from beginning I can be switched, but more likely everyone else who joined later will be switched to other team to unbalance it so well we get spawnkilled.
At least it was like this few months ago, when actually what now I consider "good speed servers" were on. Right now I stick to "PGP-only" servers and there is no autobalance I think.