JWise,
You say the trigger "seized up."
While dry firing a possibility is a short stroke, trying to pull the trigger
again before it fully returns to "reset" or firing position. Even with
strong factory springs it can be done.
When aftermarket springs are used (I know you didn't)
to achieve a much lighter DA pull, the possibility of a
short stroke increases.
Best to let the trigger finger go forward
or ease up substantially ahead of the trigger
so it can fly forward all by its lonesome.
But whatever, it sounds like an easy fix by S&W.