Well said, Stu.
The software will try to honor seat locks unless it just really has no other choice, as far as it can tell. And I'll be the first to admit the table balancing algorithm isn't perfect. But it does do a fairly good job.
Most of the time, table balancing involves moving a single player, or collapsing a table (and thus moving several players, but typically to the same table). When the software attempts to move you, is it collapsing your table, or moving just you?
Here's a scenario: There are 4 tables of 10 seats. There are 37 players left, so tables have 10, 9, 9, and 9 players. If someone busts out at the table with 10 players, nothing needs to be done, as the tables will now be 9, 9, 9, and 9. However, if a player busts out at one of the other tables, you'll have 10, 9, 9, and 8. To balance this, a player must be taken from the table with 10 players and moved to the table with 8 players. That's the only choice. So you have an option to move one of 10 players. If you have the dealer buttons set, that further reduces the choice to a single player (whomever is in the same position as the busted player, with respect to the button).
I just verified in this scenario, the software will always pick the same player (the player who is sitting in the same position wrt the dealer button). I also verified that if that player is locked, the software will choose a different player at random (from the same table). So I guess I'm not sure what's going on in your case, unless the software is collapsing the table you are sitting at.