I've been using the Heirarchy of Needs bow a lot lately, but I noticed that sometimes when you're at full stacks of Guidance Ring, and attempt to deploy it with a hipfire shot, your stacks can all get used up but the ring doesn't deploy at all. I found it happens most often when the hipfire shot connects with an enemy. It seems to happen more often when landing headshots, and even more often against the subjugators during the Salvation's Edge Witness fight, for whatever reason.