Issue:
Why does the ridge line move in an unexpected way when I override the pitch on an edge?
Solution:
Most likely your roof is set to Height above Plate (HAP) calculated. When you change the pitch of HAP calculated roof edges, it can change the Height relative to the adjacent edges, and that causes the unexpected motion of the ridge or valley line. Change the calculation method to Overhang Calculated or Plate to Fascia Calculate and the ridge line will stop moving.