Flash Bug or Latency

There has been many time where i flash but i die after or its like 0.5 seconds when i flash die but my flash gets put on a 3 second cooldown is this just the game not reacting fast enough to imput that i flashed or what is it because this happens a lot of stops me from getting away from a lot of situations. honestly its pretty tilting knowing that you did flash and it getting put on a 3 second CD after is insulting lol like hey you tried but you werent fast enough. Is this just me or does anyone else have this problem