I launched rockets with proper COM and TWR, and with aerodynamic surfaces, I am new to the game and just started making larger rockets to reach Minimus, but at about 3500m~5000m, the upper stage decouples without input(even though my stage sequence is proper) and flips the rocket ,i used the correct decoupler, with SAS engaged. yet this continues for all of the larger rockets. What is wrong here? Everything was proper for smaller rockets....