Are squads set like : "These guys must not play together" ?
On servers where autobalance has not been set to ignore squads/clans, it will put people in a squad together even at the sake of usually completely disabling autobalance.
le brilliant. (95% of servers)
On servers where autobalance is set to be able to ignore squads/clans, it can autobalance after teams are first shuffled into squads. So after a few rounds if a squad is too good, it will move people around. (5 percent of servers)
Same with clan tags (mega derp).