Might be unrelated, but I find other stuff keeps dropping out as well. One example being a quick jump onto the sparrows and boost immediately - except the boost lasts for a second and stops causing you to have to release and then press boost again to get going. Another is the quick swap to the sword and heavy attack. The sword appears and regardless of how perfect the timing is for the first heavy attack my guardian just stands there with a sword out, again it requires a release and repress of the button to actually trigger the attack. I only have two controllers but I have tried both and it has happened on both. But like you said it's not happening every time so it's hard to recreate. I wonder if it is something that has been implemented to reduce the glitches people are exploiting with the quick swap shotgun trick and other similar glitch exploit.