Split ACEs :(

My club starts shooting again from Saturday so thought I would finally check and refletch all my ACEs. I have found 5 split at the back. I shoot pins and these have split the aluminium tube but not the carbon. I suspect it is impact damage but can't get it out of my head it may be stress from string walking. If it is stress I may go to In/Out nocks to lessen it. For now I've hacked off 0.5" from the back of each arrow which will make them more twitchy but I can live with that.