Magic Keyboard with MacMail issues

I recently bought a new iMac and Magic Keyboard and am generally happy with how the transition to a new machine is going, but I can't switch over to the new machine completely because Mac Mail has gone berserk since the update to Sonoma. When typing, the cursor leaps back a word or two after typing a word then leaps ahead again. When the cursor reaches the end of the viewing box, the words pile up over one another and I can't see what I've typed. Sometimes the words also write over one another when I go back to change something I've written. As suggested in other online help forums, I've turned off "correct spelling automatically", "smart quotes", and "predictive text" but nothing helps. Plus it's a shame to lose those features. Any suggestions? And does Apple plan to do anything about these bugs?