I'm glad you are on track to finding the problem.
Using the sustain pedal did not cause my Audya to freeze. In fact nothing did. However, I only used it on one voice, or occasionally a layer of two voices, at a time. I'm certain my style of playing would never approach using up the available polyphony, even using sustain.
I also never used the midi connection function. Couldn't think of a reason to. Maybe my simpler needs were a reason that I didn't have problems.
Anyway, best wishes with this wonderful instrument.
DonM