The short answer is yes, both experience it. The longer answer is it manifests differently depending on which side you’re on.
Soul shock for the runner is interesting because they often don’t even understand what’s happening to them. They feel this deep ache but have no clue why. They haven’t done the spiritual work usually, so they’re just sitting there with all this pain and no explanation for it.
It sucks, but it is necessary to end the running/chasing cycle. If the runner didn’t feel that ache from rejecting the truth, nothing would ever make them stop and think differently. For chasers, the shock leaves you feeling bereft, confused and powerless. Some people develop resentment toward their twin, which just slows everything down.
Can it happen more than once? Yeah definitely. The roles can even reverse - runners often become chasers eventually, once the soul shock really sets in and they start dealing with their regret. Some sources say that’s karmic and part of the lesson.