Unable to switch gamemode

Was in creative, picked up all the new items in my inventory, I used gamemode switcher (F3+F4 by default) to go to the amethyst geodes. Upgraded randomTickSpeed to 30000 to see amethystes growing up. From this point, gamemode switcher and `/gamemode spectator`, didn't seemed to work. I tried to quit the game but it was unable to save & quit (freezed on saving world...). So I used `taskkill /f /im java.exe` to close minecraft