This line https://github.com/hammy3502/immersive-mc/blob/1.19.x/common/src/main/java/com/hammy275/immersivemc/common/subscribe/CommonSubscriber.java#L38 runs for all players on both sides. On the client side, this runs for other players, thus causing the crash due to the check added in mc-vr-api 3.0.0.