The first one is the main problem.

Me: "S-GPT".

It says: "What do you want to ask?"

"Me: "Why is the sky blue in one sentence."

It reads out the response. (I had to turn my sound switch on, or "Hey Siri" turns on sound regardless). It finishes talking.

Clears the screen.

Then it prompts "Want to follow-up"?

The "clears the screen" part is the serious problem. Not sure why it would do this on my iPhone and not yours.