Basically this bug has been a thing I'd say since the nexus update. It's completely random and we haven't found a way to re-produce it but basically what happens is that the person with this bug shoots or sprays his weapon and it produces no gun sounds. The only thing you hear is the bullet landing or the snaps of the bullet. This happens to any gun that is suppressed or un-suppressed. This has been a major bug since then and I'm surprised it hasn't been brought up and fixed.