Whenever you type to correct your script, Descript will try to automatically try to sync the new words to the underlying audio. When this is happening, the words will temporarily receive a dotted gray underline:
If Descript fails to automatically resync the audio and text, it will distribute the words evenly over the audio span.
If you want to get Descript to try resyncing a section of your script again, the only way to do it right now is by making changes to the script that trigger the resync process. If you want to resync a large string of a text - a sentence for example, you'll have to work quickly to extend the resync range by changing the spelling of many words... kind of like this:
It's an admittedly janky workaround, but hopefully something you never need to do.