New lessons seem to match the sentence to the audio quite well now and I don’t need to double up the chapter title now.
However lessons that have already been generated cannot be fixed without deleting the lesson and recreating it. Deleting the audio and re-adding it & generating time stamps doesn’t fix it - it has the same errors. Same with “regenerate lesson”.
The only thing that seems to fix the errors is to delete the lesson and add it back again.