I'm not sure I was clear about what I do. After brazing the seat tube to the bottom bracket as a separate unit, I assemble and then spot braze all the rest of the front triangle in my fixture. I don't separately braze another joint outside of the main triangle. The whole assembly keeps all the tubes true to the original frame design as I'm continuing to spot, align, braze, align each joint. If I understand you correctly you did not leave the whole triangle assembled as you brazed your bb to dt joint.