When you are during the survival or adventure, if you change to spectator, you will not fly.
When you dont fly at creative, this bug happens too.
Reproduce steps
1.Turn on the spectator mode in world settings
2.Set gamemode to the survival or adventure
3.Change to spectator mode
4.You will not fly
I am very uncomfortable when i use spectator mode because of this bug.
I hope to fix it.
We are not currently accepting bug reports for Spectator Mode as mentioned in the changelog.