Siri has become useless after update to 14.5.1; audible responses cut off after a word or half word

I'm having serious problems on an iPhone 11 running iOS 14.5.1. Siri's audible responses are cut off (on CarPlay or on speaker or on iPods Pro) after only a word or two, but the Siri icon remains on screen as though the digital assistant were still speaking. The problem persists even after a restart of the iPhone. The problem its persistent, but occasionally intermittent: about 9 times out of 10, Siri's response is apocopated as described; occasionally she manages to break through. Most times now (after the update to 14.5.1), I invoke Siri, ask a question like, “Hey Siri, what's the weather?" The screen shows “It's currently partly cloudy and 72°F. Expect clear skies…” etc. But Siri says, “It's cur…” and stops speaking. She sometimes keeps speaking on some “easter-egg” responses I use to test Siri's voice, e.g., “Hey Siri what's zero divided by zero?” But on others I ask “What's the airspeed velocity of an unladen swallow?” and she says, “The last…” (when she was going to say, “the last person who asked me that ended up in a crevasse.”

More seriously, this is especially annoying for composing text messages hands free, since I say “Siri tell [contact] [content of message].” Her response should say, “Your message to [contact name] says [content of message]” but now she says, “Your…“ or “Your message to…” This makes Siri pretty useless for most functions now.

All settings are turned on: Settings > Siri & Search

Listen for “Hey Siri” [on]

Press Side Button for Siri [on]

Allow Siri When Locked [on]

Siri Responses > Always

Announce Calls > Headphones & Car

Announce Messages > Announce Messages with Siri [on]; Announce Messages from: Messages [on]

Mute switch on the side of the iPhone is in the ”sound on” position