I believe that error shows up when something in your map is trying to get a player to move faster than the engine can handle, so the engine is letting you know it's slowing them down to be able to handle it. Are you launching players around at high speeds, or have really fast moving props or geometry players are interacting with? I encountered it years ago when using using trigger_pushes to catapult players around in a joke map, and I've seen it happen in various other joke maps over the years doing similar things. As far as I'm aware, it shouldn't cause any issues and you can safely ignore it.