The only time it should do this is when moving to the final table and you have the "Automatically randomize seating at the final table" setting selected (Settings button on the Tables tab).
I just tried your scenario, using tables of size 8, then with tables of size 10, and all I see is the TD trying to move players from table 3 to table 1, as it should. Are you sure it's trying to re-seat players already at table 1?