Put the summary of the bug you're having here

so when ever i am on a block I can switch from spectator mode to creative and a few seconds after you do that you can go under and then you will get stuck

how to reproduce

1. make a world with creative mode and cheats on
2.  stand on a block
3. go into spectator mode
4. then switch to creative
5. then  immediatley after that press shift and then you will be a few blocks down from were you were and you will be stuck then you will have to dig your way out