This has to do with delays between the gameproviders server and the casinos cashier server, being most probably due to the casinos server being overloaded or just a problem with the connections. On some casinos in Reel Rush I can tell 100% if a spin is going to give the free spins or not, since if the "long spin" occurs, that means the game providers server is sending the end result to the casinos cashier server, and if there is lag, the spin will take a bit longer and you will know you are not going to hit the feature.