[Crayder]

It's caused by the stream rate. Since [I'm guessing] you are using streamer and dynamic objects, the actors are streaming to the players before the objects are. So as far as the actors know, there isn't an object there for them to stand on. The same principle applies to vehicles. On thing you could do to bypass this is use a regular CreateObject for the floor or use a negative stream distance for the streamer object (which makes it static).