To do Casino Heist glitch, as you approach the final waypoint, it's best to have your phone up so you can easily spot when your UI disappears. and if the timing is correct, the host won't make anything by glitching it, only the players that remained connected to the end of session will get the reward. Casino replay glitch is tricky and has to be timed just right.
Did you time it right? it's not like Doomsday Act 2 or Cayo where you disconnect just as 'Passed' screen drops down.