Before we fix it, we must understand the wound. The original Steam version of Castle Crashers (pre-2015) used peer-to-peer networking that worked beautifully. However, after a major update intended to add new features (like the Back Off Barbarian DLC), The Behemoth introduced a new netcode that relies on deprecated Steam APIs.
WiFi interference causes "micro-stutters" that desync the game. online fix castle crashers best