When you make a gamemode selector(Like creative and adventure) than you dies, the gamemode selector will stuck at the curret gamemode when you dies before you change it by self control(Hold f3 and press f4 to choose the gamemode you want)
How do find it
Create a gamemode selectin that only needs to press f3 and f4(Like Survival and Creative)
Change to one of the gamemodes you select
Die
Press f3 and f4, you will find that you cannot change your gamamode conviently anymore before you choose the gamemode by holding f3 and press f4