Hey, just a quick question or two- do you ever use any other kind of Bluetooth or audio accessories with your iPhone? Just curious, since I had the very same problem a while back, while listening to content with my fave cheap, third party BT headphones enabled! I’d tap the mic icon, audio would pause, as it always should no matter what audio Device you have enabled- whenever an iPhones’ voice dictation is access by tapping the mic icon on default keyboard- and then I’d have same exact behavior you describe occur! It was driving me bonkers, because it would happen randomly too, not even using my headphones, or listening to anything on the phone at all! Solved the mystery, sometimes my hubby would turn them on, while I was busy in another room, and had been trying to pair & use them with his iphone. But every time he tried it never worked because they would auto connect to mine! Even though the mic is terrible, The audio is boss for how cheap & comfy they are, & much better than his expensive fancy ones! He’s not really allowed to use mine, because his head is much bigger, and every time he would try them on-they sound like they’re gonna crack in half!! 😂. Seriously thought there was a ghost in the machine, before we figured it out! Frequently, whenever those were on & auto connected to my iPhone, before we figured out the culprit, the text that did pop up successfully, were words that were entirely different, not even similar sounding words, to mine!
I do know that the type of behavior you are seeing can also be software related, or only occurs when using VD with certain third party apps!
Especially since all of the upgrades in privacy and security features released, with our more recent iOS/iPadOS software versions, it’s imperative to keep your software updated to keep that microphone, and VD feature working smoothly!
Have you tried updating your iOS software? Or any other troubleshooting steps like recording a Voice memo, to be sure your mic is Working as it should?
If so, double check that you have voice dictation enabled, in Settings, General, Scroll down until you see keyboard cabinet and make sure the toggle switch is on, for Enable Dictation! If it is on already, I’d say try force restarting your iPhone, Just to give it a nice refresh! Just be sure to use the correct process for your iPhone, found here: https://support.apple.com/guide/iphone/force-restart-iphone-iph8903c3ee6/ios
I hope that helps! If not, definitely reach out to Apple Support directly via chat or phone to report it! Your device may need more extensive troubleshooting or service!