Hi Mark, that's not a great experience, hope I can identify the problem and resolve it asap!
Just to make sure: after running autofill, once the grid has been fully filled, the suggested letters are shown in gray. Then, from the autofill panel (you can reopen it if's closed), you have to click on the "Accept" button to say that you're OK with the suggested fills. Then the letters will be in black font instead of gray.
Please confirm that you are already doing this (if not, this should fix your problem).
If you can record a short video that shows the problem, that can be useful. You can share it with me at
vir...@gmail.com. please also let me know what platform you're using (browser and device).
Thanks,
Viresh