The problem was that the raycasts would hit the interpolated hitboxes instead of the players. I either did something to ignore the interpolated hitboxes or make them register as the player entities to fix that. I'm not sure how that fix failed to work in the linux version. It's pretty easy to tell when it's happening, though. If somebody is moving toward you, it will register (because the interpolated hitbox is behind them), and if he's moving away from you, it won't register (because the interpolated hitbox is between you and him).
Guess I'll have to look into that when I get back home after the new year.