John,
You didn't say what type of aircraft, but look for air getting into the
spoiler boxes and pushing the top out into the slipstream. I am assuming
they are not unlocking, only the springs compressing.

This often comes from not having a good seal at the wing roots and air
pressure is finding its way through the wing and into the spoiler boxes.
As soon as they come up a bit, the slipstream will catch them and pull the
top out further.