I hear what your sayin but, for the stiffer spring to compress the same amount as the light spring requires more pressure, i.e. weight in this case.
that t-bar socket was compromised somehow whether it be crappy build from the factory, somehow hammered in its previous life (think Dukes of Hazzard), plain old metal fatigue or something.
the bigger bars probably just made that socket fail sooner rather than later.
