FYI I understand elbow glitch is a more serious problem. We are working on that too but it is complicated. The up/down was just a code bug, which one of our Programmers could fix by themselves. The elbow glitch requires adjusting the shooting-pose animation when in prone; which in turn requires the redoing of many related animations (reloading, for example, since it blends into the prone pose).
We will fix it, it's important, so we don't mind putting in that work, but I do ask for your patience on this one.