Hard to say?
What does the pedal feel like when juddering? soft then hard?
Did it do this before the disc and pad change?
It could be pockets of air traped in the system?
Sometimes the Master cylinder seals can wear out and cause uneven pressure kind of acting like ABS presure no pressure.
I think I would bleed the whole system out again, check all union bolts for leaks, then check bolts are tight on the carrier.
Check all hose lines for flexing.
If all is good it can only be the MC?
If it was servo you would feel lack of pedal feel even if the servo vac boost pipe had come off the head.
