I made a vidoe showing off what I think you're trying to say, and I hope it helps.
I'm not really sure, I've never had this happen to me before, if you could give a little bit more detail on when the bug occurs for example, after a long time when playing, when you just start the game, etc.
If you could give a little bit more detail on what is happening that would be helpful but from what I've gathered you are probably playing on a server that doesn't have phantoms enabled, if you're not then I don't really know all I can really say is please supply some more information about this. Thank you!
This isn't a bug.
I haven't experienced this problem so it must be because to your computer not being good enough to run Minecraft.
Yes, this is caused by the little bit of invulnerability you get when you join a game.
It sounds like your mouse is broken, or your computer just can't run Minecraft that well.
This isn't a bug its how the game was designed, you wouldn't want all your bone meal going to waste for no reason now would you?
Were you playing with any mods at the time?
If you find the issue again please screenshot it and send it as proof. Also snapshots aren't the most stable versions of Minecraft which is why they're deactivated by default, if you want a smoother more non-buggy game I recommend disabling them and playing on the latest release.
This is not a bug, the reason you have this problem is because you have a bad connection to the realm. Sorry to hear about your situation.
I'll check in 20w14a
Edit: in 20w14a the bug does not take place so this is resolved