I spoke with Remedy Support about this once. They said because SLAs are "buggy", they can only handle One Notification, and one action. That means if you have an SLA with 5 actions, each action will fire 5 times. An interim solution is to put the actions in a separate SLA (using the same Terms & Conditions). They said this was a problem with SLA 5.0 and should be fixed with their newer release of SLA (no release date).
It's a bit of work for the SLAs, but I did notice them working correctly once I set them up separately.
Hope this helps,
Bryan