siri doesn't listen after responding

The steps are simple to reproduce this. Simply ask anything of Siri and wait for a response.

Siri wakes up, responds (on the screen and with audio), there's the Siri "button" at the bottom of the screen... but I can't ask her another question. "hey siri" doesn't work. Any organic/natural question doesn't work. I have to manually press the button - even if I initiated the original question with "hey siri"

How can I get Siri to continue a conversation without manual intervention to ask/state subsequent commands/questions?

In the example below my phone as locked and I said "hey siri, what time is it?". She responded, showed and said the time, and then.... the phone is stuck. I can't do anything else with just audio.