One way to avoid this is to work in smaller units and then join the smaller units to make your panel.
If your panel has 24 strips, sew 12 sets of 2 strips. Then sew the strip pairs together in pairs, so you have 6 sets of 4 strips. Then join those so you have 3 sets of 8 strips. Sew the 3 units together. By working with larger, more stable units, you are less likely to pull them out of shape.