When Weapon::Fire is used to fire a gun on server, then the damage done by consecutively fired shots sometimes gets applied to a previously hit entity (this is also true for the associated firearm effects like blood splatter etc), especially if that entity died from a previously fired shot. The wrongly damaged entity can even be hundreds of meters away or behind objects that are not penetrable by projectiles, which seems to indicate that the damage is just applied to some cached reference of that previously hit entity.
As a side note, tracing the actual projectile trajectory also indicates that the projectile indeed does travel in the intended direction and not to the entity that wrongly receives the damage, which seems to indicate the fired projectile itself is probably not the issue.