Happened to me a few days ago. You are using get component / set property and modify de fov, right?
There's some kind of live reference to the camera that works in the editor, but the build doesn't like.
Instead, try "Get main camera action" and then "Set camera FoV" action. I'm using this for a "zoom" and it works perfectly.
I don't remember if "Set camera FoV" comes with vanilla playmaker, if not, search here and download the action.
Cheers.