When you change the zoom settings in Google docs, it changes the context it is sending to the Co:Writer extension. The new context is not reporting the proper cursor location to the Co:Writer extension causing the last letter to be deleted.
To resolve this issue:
1. Set the Zoom function in Google docs to 100% (if it is already at 100% go to 90% then back to 100%)
2. Click on the Google 'Customize and Control Google Chrome Button" in the upper right hand corner of your Chrome Browser.
3. Go to zoom and set it to 100%
4. Refresh the page.
If you need the Zoom function use the browsers zoom.
1. Click on the Google 'Customize and Control Google Chrome' slider bar .
2. Go down to zoom - and adjust your zoom settings here.